Liner Design to Reduce Unburned Hydrocarbon Exhaust Emissions

2018 ◽  
Author(s):  
Paul S. Wang ◽  
Allen Y. Chen
Keyword(s):  
Natural Gas ◽  
Ventilation System ◽  
Hydrocarbon Emissions ◽  
Tracer Technique ◽  
Oil Consumption ◽  
Natural Gas Engines ◽  
Unburned Hydrocarbon ◽  
Crankcase Ventilation ◽  
Unburned Fuel ◽  
Careful Design

Large natural gas engines that introduce premixed fuel and air into the engine cylinders allow a small fraction of fuel to evade combustion, which is undesirable. The premixed fuel and air combust via flame propagation. Ahead of the flame front, the unburned fuel and air are driven into crevices, where conditions are not favorable for oxidation. The unburned fuel is a form of waste and a source of potent greenhouse gas emissions. A concept to vent unburned fuel into the crankcase through built-in slots in the liner during the expansion stroke has been tested. This venting process occurs before the exhaust valve opens and the unburned fuel sent into the crankcase can be recycled to the intake side through a closed crankcase ventilation system. The increased communication between the cylinder and the crankcase changes the ring pack dynamics, which results in higher oil consumption. Oil consumption was measured using a sulfur tracer technique. Careful design is required to achieve the best tradeoff between reductions in unburned hydrocarbon emissions and oil control.

Potential Reduction of Fugitive Methane Emissions at Compressor Stations and Storage Facilities Powered by Natural Gas Engines

2014 ◽  
Author(s):  
Derek Johnson ◽  
April Covington
Keyword(s):  
Natural Gas ◽  
Methane Emissions ◽  
Hydrocarbon Emissions ◽  
Storage Tanks ◽  
Lean Burn ◽  
Potential Reduction ◽  
Natural Gas Engines ◽  
Crankcase Ventilation ◽  
And Storage ◽  
Storage Facilities

The American Gas Association (AGA) and the United States (US) Energy Information Administration (EIA) report that natural gas reserves, production, and consumption are increasing. Current estimates show over 100 years worth of recoverable reserves. As production increases, the natural gas pipeline interstate will grow or at least experience increased throughput. With the industry expanding at rapid rates and the high global warming potential of methane (21 over a 100 year period), it is important to identify potential sources for reductions in fugitive methane emissions. This research group conducted leak and loss audits at five natural gas compressor station and storage facilities. The majority of methane losses were associated with the operation of the lean-burn, natural gas engines (open crankcases, exhaust), compressor seal vents, and open liquid storage tanks. This paper focuses on the potential reduction in fugitive methane emissions of the discovered industry weaknesses through application of various proven technologies. As engines are not perfectly sealed, blow-by of intake air, fuel, and combustion gases occurs past the piston rings. In order to prevent a build-up of pressure within the crankcase, it must be vented. Diesel engines have lower hydrocarbon emissions from their crankcases due to the short duration of fuel addition after compression of the intake charge. Lean-burn, natural gas engines, like conventional gasoline engines, compress both the fuel and intake air during the compression stroke. During the 1960s, many passenger vehicles adopted positive crankcase ventilation (PCV) or closed crankcase ventilation (CCV) systems to reduce significantly hydrocarbon emissions from engines. Currently, some heavy-duty on-road engines still have open crankcase systems and most off-road engines have crankcases simply vented to the atmosphere. In this paper, researchers will examine the potential reduction in methane emissions that could be realized with the installation of retrofitted CCV systems at these locations. In addition to the reduction of methane losses from the crankcase, it is realized that with proper plumbing, flow control, and safety parameters, all of the losses typically vented to atmosphere could be ducted into the engine intake for combustion. Preliminary results show that applications of closed crankcase systems could reduce emissions from these sites by 1–11% while modifying these systems to include the losses from compressor seal vents and storage tanks could yield potential reductions in methane emissions by 10–57%.

The Advanced Injection Low Pilot Ignited Natural Gas Engine: A Combustion Analysis

2003 ◽  
Author(s):  
Kalyan K. Srinivasan ◽  
Sundar R. Krishnan ◽  
Sabir Singh ◽  
K. Clark Midkiff ◽  
Stuart R. Bell ◽  
...  
Keyword(s):  
Natural Gas ◽  
Natural Gas Engines ◽  
Natural Gas Engine ◽  
Unburned Hydrocarbon ◽  
Full Load Operation ◽  
Dual Fuel Engines ◽  
Engine Stability ◽  
Hc Emissions ◽  
Conversion Efficiencies ◽  
Diesel Operation

The Advanced Low Pilot Ignited Natural Gas (ALPING) engine is proposed as an alternative to diesel and conventional dual fuel engines. Experimental results from full load operation at a constant speed of 1700 rev/min are presented in this paper. The potential of the ALPING engine is realized in reduced NOx emissions (less than 0.2 g/kWh) at all loads accompanied by fuel conversion efficiencies comparable to straight diesel operation. Some problems at advanced injection timings are recognized in high unburned hydrocarbon (HC) emissions (25 g/kWh), poor engine stability reflected by high COVimep (about 6 percent), and tendency to knock. This paper focuses on the combustion aspects of low pilot ignited natural gas engines with particular emphasis on advanced injection timings (45°–60°BTDC).

Two-Stage Lean-Burn Combustion Inside a Natural-Gas Spark-Ignition Engine With a Bowl-in-Piston Chamber

2019 ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Combustion Process ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Intake Manifold ◽  
Hydrocarbon Emissions ◽  
Fuel Injector ◽  
Unburned Hydrocarbon ◽  
Piston Chamber

Abstract The conversion of existing diesel engines to spark ignition (SI) operation by adding a low-pressure injector in the intake manifold for fuel delivery and replacing the original high-pressure fuel injector with a spark plug to initiate and control the combustion process can reduce U.S. dependence on petroleum imports and increase natural gas (NG) applications in heavy-duty transportation sectors. Since the conventional diesel combustion chamber (i.e., flat-head-and-bowl-in-piston-chamber) creates high turbulence, the converted NG SI engine can operate leaner with stable and repeatable combustion process. However, existing literatures point to a long late-combustion duration and increased unburned hydrocarbon emissions in such retrofitted engines that maintained the original combustion chamber. Consequently, the main objective of this paper was to report recent findings of NG combustion characteristics inside a bowl-in-piston combustion chamber that will add to the general understanding of the phenomena. The new results indicated that the premixed NG burn inside the bowl-in-piston combustion chamber will separate into a bowl-burn and a squish-burn processes in terms of burning location and timing. The slow burning event in the squish region explains the low slope of the burn rate towards the end of combustion in existing studies (hence the longer late-combustion period). In addition, the less-favorable conditions for the combustion in the squish region explained the increased carbon monoxide and unburned hydrocarbon emissions.

Blow-By Truck Application: Electrically Driven Cone Stack Separator for Crankcase Ventilation

2007 ◽  
Author(s):  
Gerd Kissner ◽  
Hartmut Sauter
Keyword(s):  
Separation Efficiency ◽  
Ventilation System ◽  
Motor Vehicles ◽  
Cylinder Wall ◽  
Oil Consumption ◽  
Control Laws ◽  
Crankcase Ventilation ◽  
Oil Fraction ◽  
Air Intake ◽  
Oil Mist

Dealing with the blow-by gas from reciprocating engine is a bigger challenge nowadays due to strict emission control laws and design limitations. Blow-by gas originates between the piston or piston rings and the cylinder wall and is charged with oil when it leaves the crankcase. In a closed crankcase ventilation system these blow-by gases are drawn from the crankcase into the air intake. The oil mist separator (OMS) retains a fraction of the liquid oil and returns the retained oil fraction back to the oil sump. Thus, the oil mist separator reduces oil consumption and emissions. Electrically driven cone stack separators have high separation efficiency, small differential pressure, arbitrary mounting position and low power consumption. In addition to that, the electrically driven cone stack separator has also advantageous control characteristics. Since commercial motor vehicles already have high electrical system requirements a Mechatroic concept is presented here which was developed to be maintenance-free over the lifetime of the engine. This is achieved by detailed design and choice of special materials. In this paper, the construction and application of the novel oil mist separator system for trucks are discussed in detail.

Effect of Ring Dynamics and Crevice Flows on Unburned Hydrocarbon Emissions

1994 ◽  
Vol 116 (4) ◽  
pp. 784-792 ◽  
Author(s):  
L. K. Shih ◽  
D. N. Assanis
Keyword(s):  
Internal Combustion Engines ◽  
Gasoline Engine ◽  
Design Parameters ◽  
Fuel Vapor ◽  
Hydrocarbon Emissions ◽  
Reacting Flow ◽  
Piston Cylinder ◽  
Unburned Hydrocarbon ◽  
Ring Assembly ◽  
Unburned Fuel

A significant source of unburned hydrocarbon emissions from internal combustion engines originates from the flow of unburned fuel/air mixture into and out of crevices in the piston-cylinder-ring assembly. During compression, fuel vapor flows into crevice regions. After top dead center, the trapped fuel vapor that returns into the cylinder escapes complete oxidation and contributes to unburned hydrocarbon emissions. In this work, the crevice flow model developed by Namazian and Heywood is implemented into KIVA-II, a multidimensional, reacting flow code. Two-dimensional, axisymmetric simulations are then performed for a 2.5 liter gasoline engine to investigate the effects of engine speed and selected piston-ring design parameters on crevice flows and on unburned hydrocarbon emissions. Results suggest that engine-out unburned hydrocarbon emissions can be reduced by optimizing the ring end gap area and the piston-cylinder side clearance.

Effects of Natural Gas Compositions on Engine In-Cylinder Process

2015 ◽  
Vol 1092-1093 ◽  
pp. 498-503
Author(s):  
La Xiang ◽  
Yu Ding
Keyword(s):  
Natural Gas ◽  
Alternative Fuels ◽  
Combustion Process ◽  
Engine Performance ◽  
Maximum Temperature ◽  
Maximum Pressure ◽  
Test Bed ◽  
Promising Alternative ◽  
Natural Gas Engines ◽  
Lower Maximum

Natural gas (NG) is one of the most promising alternative fuels of diesel and petrol because of its economics and environmental protection. Generally the NG engine share the similar structure profile with diesel or petrol engine but the combustion characteristics of NG is varied from the fuels, so the investigation of NG engine combustion process receive more attentions from the researchers. In this paper, a zero-dimensional model on the basis of Vibe function is built in the MATLAB/SIMULINK environment. The model provides the prediction of combustion process in natural gas engines, which has been verified by the experimental data in the NG test bed. Furthermore, the influence of NG composition on engine performance is investigated, in which the in-cylinder maximum pressure and temperature and mean indicated pressure are compared using different type NG. It is shown in the results that NG with higher composition of methane results in lower maximum temperature and mean indicated pressure as well as higher maximum pressure.

Advantages of the unscavenged pre-chamber ignition system in turbocharged natural gas engines for automotive applications

Energy ◽  
2021 ◽  
Vol 218 ◽  
pp. 119466
Author(s):  
J.J. López ◽  
R. Novella ◽  
J. Gomez-Soriano ◽  
P.J. Martinez-Hernandiz ◽  
F. Rampanarivo ◽  
...  
Keyword(s):  
Natural Gas ◽  
Automotive Applications ◽  
Ignition System ◽  
Natural Gas Engines

Transient Behavior of Glow Plugs in Direct-Injection Natural Gas Engines

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Stewart Xu Cheng ◽  
James S. Wallace
Keyword(s):  
Heat Transfer ◽  
Natural Gas ◽  
Direct Injection ◽  
High Surface ◽  
Cold Start ◽  
Transfer Model ◽  
Ignition Process ◽  
Computational Domain ◽  
Glow Plug ◽  
Natural Gas Engines

Glow plugs are a possible ignition source for direct injected natural gas engines. This ignition assistance application is much different than the cold start assist function for which most glow plugs have been designed. In the cold start application, the glow plug is simply heating the air in the cylinder. In the cycle-by-cycle ignition assist application, the glow plug needs to achieve high surface temperatures at specific times in the engine cycle to provide a localized source of ignition. Whereas a simple lumped heat capacitance model is a satisfactory representation of the glow plug for the air heating situation, a much more complex situation exists for hot surface ignition. Simple measurements and theoretical analysis show that the thickness of the heat penetration layer is small within the time scale of the ignition preparation period (1–2 ms). The experiments and analysis were used to develop a discretized representation of the glow plug domain. A simplified heat transfer model, incorporating both convection and radiation losses, was developed for the discretized representation to compute heat transfer to and from the surrounding gas. A scheme for coupling the glow plug model to the surrounding gas computational domain in the KIVA-3V engine simulation code was also developed. The glow plug model successfully simulates the natural gas ignition process for a direct-injection natural gas engine. As well, it can provide detailed information on the local glow plug surface temperature distribution, which can aid in the design of more reliable glow plugs.

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