Using Geared Mechanisms to Increase the Thermal Efficiency of Conventional IC-Engines

1994 ◽  
Author(s):  
David N. Rocheleau
Keyword(s):  
Internal Combustion Engine ◽  
Thermal Efficiency ◽  
Atmospheric Pressure ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Constant Volume ◽  
Power Stroke ◽  
Stroke Length ◽  
Constant Volume Combustion ◽  
Ic Engines

Abstract Two different geared mechanisms are examined as an alternative to the conventional crank-slider mechanism that is used for the 4-stroke internal combustion engine. The purpose of these geared mechanisms is to provide variable-stroke length and constant-volume combustion. The variable-stroke length feature gives a power stroke which is two to three times longer than the compression stroke, which allows additional work to be extracted as the gas expands to nearly atmospheric pressure. The constant-volume combustion feature prevents the dissipation of compressive work during ignition. The combination of these two features leads to theoretical thermal efficiency gains of up to 45% over the standard fixed-stroke length Otto-cycle internal combustion engine.

Designing of a Balanced Opposed Piston Engine

2016 ◽  
Vol 852 ◽  
pp. 719-723
Author(s):  
Sunil S. Hebbalkar ◽  
Kaushik Kumar
Keyword(s):  
Internal Combustion Engine ◽  
Power Density ◽  
Combustion Engine ◽  
Analytical Calculation ◽  
Internal Combustion ◽  
Power Stroke ◽  
Piston Engine ◽  
Crank Angle ◽  
Higher Power ◽  
Inertia Forces

An internal combustion engine with opposed piston engine (OPE) develops higher power density than any other conventional internal combustion engine by virtue of its design. A Two stroke OPE gives two power stroke within 3600 of crank revolution which indicates the higher power density. But this extra power also results in large amount of forces gets transmitted to both the crankshaft amounting to large unbalance in the engine. Hence for a smoother and noise free performance, engine should be dynamically balanced. So balancing is one of the main criteria for better performance. In this paper the dynamic analysis was performed by varying the linkage dimensions of OPE for balance OPE. The analytical calculation of inertia forces and dimensions for linkages has been compared with software based results, depending on pressure crank angle plot for two stroke engine.

The Benefits of an Inverted Brayton Bottoming Cycle as an Alternative to Turbocompounding

2015 ◽  
Vol 138 (7) ◽  
Author(s):  
Colin D. Copeland ◽  
Zhihang Chen
Keyword(s):  
Internal Combustion Engine ◽  
Thermal Efficiency ◽  
Heat Recovery ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Critical Parameters ◽  
Specific Power ◽  
Brayton Cycle ◽  
Exhaust Gas ◽  
Otto Cycle

The exhaust gas from an internal combustion engine contains approximately 30% of the thermal energy of combustion. Waste heat-recovery systems aim to reclaim a proportion of this energy in a bottoming thermodynamic cycle to raise the overall system thermal efficiency. The inverted Brayton cycle (IBC) considered as a potential exhaust-gas heat-recovery system is a little-studied approach, especially when applied to small automotive power plants. Hence, a model of an air-standard, irreversible Otto cycle and the IBC using finite-time thermodynamics (FTT) is presented to study heat recovery applied to an automotive internal combustion engine. The other two alternatives power cycles, the pressurized Brayton cycle and the turbocompounding system (TS), are compared with the IBC to specify the strengths and weaknesses of three alternative cycles. In the current paper, an irreversible Otto-cycle model with an array of losses is used as a base for the bottoming cycle. The deviation of the turbomachinery from the idealized behavior is described by the isentropic component efficiencies. The performance of the system as defined as the specific power output and thermal efficiency is considered using parametric studies. The results show that the performance of the IBC can be positively affected by five critical parameters—the number of compression stages, the cycle inlet temperature and pressure, the isentropic efficiency of the turbomachinery, and the effectiveness of the heat exchanger. There exists an optimum pressure ratio across the IBC turbine that delivers the maximum specific power. In view of the specific power, installing a single-stage of the IBC appears to be the best balance between performance and complexity. Three alternative cycles are compared in terms of the thermal efficiency. The results indicate that the pressurized and IBCs can improve the performance of the turbocharged engine (TCE) only when the turbomachinery efficiencies are higher than a value which changes with the operating condition. High performance of the IBC turbomachinery is required to ensure that the TCE with the IBC is superior to that with TS.

The Benefits of an Inverted Brayton Bottoming Cycle as an Alternative to Turbo-Compounding

2015 ◽  
Author(s):  
Colin D. Copeland ◽  
Zhihang Chen
Keyword(s):  
Internal Combustion Engine ◽  
Thermal Efficiency ◽  
Heat Recovery ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Critical Parameters ◽  
Specific Power ◽  
Brayton Cycle ◽  
Exhaust Gas ◽  
Otto Cycle

The exhaust gas from an internal combustion engine contains approximately 30% of the thermal energy of combustion. Waste heat recovery systems aim to reclaim a proportion of this energy in a bottoming thermodynamic cycle to raise the overall system thermal efficiency. The inverted Brayton cycle considered as a potential exhaust-gas heat-recovery system is a little-studied approach, especially when applied to small automotive power-plants. Hence, a model of an air-standard, irreversible Otto-cycle and the inverted Brayton cycle using finite-time thermodynamics (FTT) is presented to study heat recovery applied to an automotive internal combustion engine. The other two alternatives power cycles, the pressurized Brayton cycle and the turbo-compounding system, are compared with the inverted Brayton cycle (IBC) to specify the strengths and weaknesses of three alternative cycles. In the current paper, an irreversible Otto-cycle model with an array of losses is used as a base for the bottoming cycle. The deviation of the turbomachinery from the idealized behavior is described by the isentropic component efficiencies. The performance of the system as defined as the specific power output and thermal efficiency is considered using parametric studies. The results show that the performance of the inverted Brayton cycle can be positively affected by five critical parameters — the number of compression stages, the cycle inlet temperature and pressure, the isentropic efficiency of the turbomachinery and the effectiveness of the heat exchanger. There exists an optimum pressure ratio across the IBC turbine that delivers the maximum specific power. In the view of the specific power, installing a single-stage of the inverted Brayton cycle appears to be the best balance between performance and complexity. Three alternative cycles are compared in terms of the thermal efficiency. The results indicate that the pressurized and inverted Brayton cycles can improve the performance of the turbocharged engine only when the turbomachinery efficiencies are higher than a value which changes with the operating condition. High performance of the IBC turbomachinery is required to ensure that the turbocharged engine with the inverted Brayton cycle is superior to that with turbo-compounding system.

scholarly journals Exhaust gas heat recovery through secondary expansion cylinder and water injection in an internal combustion engine

2017 ◽  
Vol 21 (1 Part B) ◽  
pp. 729-743
Author(s):  
Toosi Nassiri ◽  
Amir Kakaee ◽  
Hazhir Ebne-Abbasi
Keyword(s):  
Internal Combustion Engine ◽  
Thermal Efficiency ◽  
Combustion Engine ◽  
Water Injection ◽  
Internal Combustion ◽  
Exhaust Gas ◽  
Exhaust Gases ◽  
Injection Process ◽  
Direct Water Injection ◽  
Novel Concept

To enhance thermal efficiency and increase performance of an internal combustion engine, a novel concept of coupling a conventional engine with a secondary 4-stroke cylinder and direct water injection process is proposed. The burned gases after working in a traditional 4-stroke combustion cylinder are transferred to a secondary cylinder and expanded even more. After re-compression of the exhaust gases, pre-heated water is injected at top dead center. The evaporation of injected water not only recovers heat from exhaust gases, but also increases the mass of working gas inside the cylinder, therefore improves the overall thermal efficiency. A 0-D/1-D model is used to numerically simulate the idea. The simulations outputs showed that the bottoming cycle will be more efficient at higher engines speeds, specifically in a supercharged/turbocharged engine, which have higher exhaust gas pressure that can reproduce more positive work. In the modeled supercharged engine, results showed that brake thermal efficiency can be improved by about 17%, and brake power by about 17.4%.

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