Comparing Cetane Number Measurement Methods

2020 ◽  
Author(s):  
Riley C. Abel ◽  
Jon Luecke ◽  
Matthew A. Ratcliff ◽  
Bradley T. Zigler
Keyword(s):  
High Pressure ◽  
Diesel Engines ◽  
Ignition Delay ◽  
High Efficiency ◽  
Performance Metrics ◽  
Fuel Injection ◽  
Cetane Number ◽  
Compression Ignition ◽  
Fuel Performance ◽  
Compression Type

Abstract Cetane number is one of the most important fuel performance metrics for mixing controlled compression-ignition “diesel” engines, quantifying a fuel’s propensity for autoignition when injected into end-of-compression-type temperature and pressure conditions. The historical default and referee method on a Cooperative Fuel Research (CFR) engine configured with indirect fuel injection and variable compression ratio is cetane number (CN) rating. A subject fuel is evaluated against primary reference fuel blends, with heptamethylnonane defining a low-reactivity endpoint of CN = 15 and hexadecane defining a high-reactivity endpoint of CN = 100. While the CN scale covers the range from zero (0) to 100, typical testing is in the range of 30 to 65 CN. Alternatively, several constant-volume combustion chamber (CVCC)-based cetane rating devices have been developed to rate fuels with an equivalent derived cetane number (DCN) or indicated cetane number (ICN). These devices measure ignition delay for fuel injected into a fixed volume of high-temperature and high-pressure air to simulate end-of-compression-type conditions. In this study, a range of novel fuel compounds are evaluated across three CVCC methods: the Ignition Quality Tester (IQT), Fuel Ignition Tester (FIT), and Advanced Fuel Ignition Delay Analyzer (AFIDA). Resulting DCNs and ICNs are compared for fuels within the normal diesel fuel range of reactivity, as well as very high (∼100) and very low DCNs/ICNs (∼5). Distinct differences between results from various devices are discussed. This is important to consider because some new, high-efficiency advanced compression-ignition (CI) engine combustion strategies operate with more kinetically controlled distributed combustion as opposed to mixing controlled diffusion flames. These advanced combustion strategies may benefit from new fuel chemistries, but current rating methods of CN, DCN, and ICN may not fully describe their performance. In addition, recent evidence suggests ignition delay in modern on-road diesel engines with high-pressure common rail fuel injection systems may no longer directly correlate to traditional CN fuel ratings. Simulated end-of-compression conditions are compared for CN, DCN, and ICN and discussed in the context of modern diesel engines to provide additional insight. Results highlight the potential need for revised and/or multiple fuel test conditions to measure fuel performance for advanced CI strategies.

Implementation Challenges and Solutions for Homogenous Charge Compression Ignition Combustion in Diesel Engines

2014 ◽  
Author(s):  
Usman Asad ◽  
Ming Zheng ◽  
David Ting ◽  
Jimi Tjong
Keyword(s):  
High Pressure ◽  
Diesel Engines ◽  
Performance Metrics ◽  
Pressure Rise ◽  
Engine Performance ◽  
Injection Pressure ◽  
Combustion Stability ◽  
Compression Ignition ◽  
Hcci Combustion ◽  
Homogenous Charge Compression Ignition

Homogenous charge compression ignition (HCCI) combustion in diesel engines can provide for cleaner operation with ultra-low NOx and soot emissions. While HCCI combustion has generated significant attention in the last decade, however, to date, it has seen very limited application in production diesel engines. HCCI combustion is typically characterized by earlier than top-dead-center (pre-TDC) phasing, very high pressure rise rates, short combustion durations and minimal control over the timing of the combustion event. To offset the high reactivity of the diesel fuel, large amounts of EGR (30 to 60%) are usually applied to postpone the initiation of combustion, shift the combustion towards TDC and alleviate to some extent, the high pressure rise rates and the reduced energy efficiency. In this work, a detailed analysis of HCCI combustion has been carried out on a high-compression ratio, single-cylinder diesel engine. The effects of intake boost, EGR quantity/temperature, engine speed, injection scheduling and injection pressure on the operability limits have been empirically determined and correlated with the combustion stability, emissions and performance metrics. The empirical investigation is extended to assess the suitability of common alternate fuels (n-butanol, gasoline and ethanol) for HCCI combustion. On the basis of the analysis, the significant challenges affecting the real-world application of HCCI are identified, their effects on the engine performance quantified and possible solutions to overcome these challenges explored through both theoretical and empirical investigations. This paper intends to provide a comprehensive summary of the implementation issues affecting HCCI combustion in diesel engines.

Implementation Challenges and Solutions for Homogeneous Charge Compression Ignition Combustion in Diesel Engines

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Usman Asad ◽  
Ming Zheng ◽  
David S.-K. Ting ◽  
Jimi Tjong
Keyword(s):  
High Pressure ◽  
Diesel Engines ◽  
Homogeneous Charge Compression Ignition ◽  
Performance Metrics ◽  
Pressure Rise ◽  
Injection Pressure ◽  
Combustion Stability ◽  
Compression Ignition ◽  
Hcci Combustion ◽  
Homogeneous Charge

Homogeneous charge compression ignition (HCCI) combustion in diesel engines can provide cleaner operation with ultralow NOx and soot emissions. While HCCI combustion has generated significant attention in the last decade, however, till date, it has seen very limited application in production diesel engines. HCCI combustion is typically characterized by earlier than top-dead-center (pre-TDC) phasing, very high-pressure rise rates, short combustion durations, and minimal control over the timing of the combustion event. To offset the high reactivity of the diesel fuel, large amounts of exhaust gas recirculation (EGR) (30–60%) are usually applied to postpone the initiation of combustion, shift the combustion toward TDC, and alleviate to some extent, the high-pressure rise rates and the reduced energy efficiency. In this work, a detailed analysis of HCCI combustion has been carried out on a high-compression ratio (CR), single-cylinder diesel engine. The effects of intake boost, EGR quantity/temperature, engine speed, injection scheduling, and injection pressure on the operability limits have been empirically determined and correlated with the combustion stability, emissions, and performance metrics. The empirical investigation is extended to assess the suitability of common alternate fuels (n-butanol, gasoline, and ethanol) for HCCI combustion. On the basis of the analysis, the significant challenges affecting the real-world application of HCCI are identified, their effects on the engine performance quantified, and possible solutions to overcome these challenges explored through both theoretical and empirical investigations. This paper intends to provide a comprehensive summary of the implementation issues affecting HCCI combustion in diesel engines.

High-Pressure Electronic Fuel Injection for Small-Displacement Single-Cylinder Diesel Engines

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Andrew L. Carpenter ◽  
Robert E. Mayo ◽  
Jerald G. Wagner ◽  
Paul E. Yelvington
Keyword(s):  
High Pressure ◽  
Diesel Engines ◽  
Fuel Injection ◽  
Cetane Number ◽  
Injection Pressure ◽  
Injection System ◽  
Orifice Diameter ◽  
Small Displacement ◽  
Single Cylinder ◽  
Injection Parameters

Small-displacement single-cylinder diesel engines employ mechanically actuated fuel injection systems. These mechanically governed systems, while robust and low cost, lack the ability to fully vary injection parameters, such as timing, pulse duration, and injection pressure. The ability of a particular injection system to vary these injection parameters impacts engine efficiency, power, noise, and emissions. Modern, multicylinder automotive engines employ some form of electronically controlled injection to take advantage of the benefits of fully variable injection, including advanced strategies such as multipulse injections and rate shaping. Modern diesel electronic fuel injection (EFI) systems also operate at considerably higher injection pressures than mechanical fuel systems used in small-bore industrial engines. As the cost of electronic fuel systems continues to decrease and the demand for high-efficiency engines increases, EFI becomes a more viable option for incorporation into small industrial diesel engines. In particular, this technology may be well-suited for demanding and critical applications, such as military power generation. In this study, a small-bore single-cylinder diesel was retrofit with a custom high-pressure EFI system. Compared to the mechanical injector, the electronic, common-rail injector had a 50% smaller orifice diameter and was designed for a fourfold higher injection pressure. The mechanical governor was also replaced with an electronic speed controller. The baseline and modified engines were installed on a dynamometer, and measurements of exhaust emissions, fuel consumption, brake torque, and in-cylinder pressure were made. The electronic injector leads to lower smoke opacity and NOx emissions, while CO and hydrocarbon emissions were observed to increase slightly, likely due to some wall wetting of fuel with the initial prototype injector. Testing with low ignition quality fuels was also performed, and the electronic fuel system enabled the engine to operate with fuel having a cetane number as low as 30.

Effect of n-heptane and n-decane on exhaust odour in direct injection diesel engines

2005 ◽  
Vol 219 (4) ◽  
pp. 565-571 ◽  
Author(s):  
M M Roy
Keyword(s):  
Direct Effect ◽  
Diesel Fuel ◽  
Diesel Engines ◽  
Ignition Delay ◽  
Boiling Point ◽  
Alternative Fuels ◽  
Direct Injection ◽  
Cetane Number ◽  
Mixture Formation ◽  
Incomplete Combustion

This study investigated the effect of n-heptane and n-decane on exhaust odour in direct injection (DI) diesel engines. The prospect of these alternative fuels to reduce wall adherence and overleaning, major sources of incomplete combustion, as well as odorous emissions has been investigated. The n-heptane was tested as a low boiling point fuel that can improve evaporation as well as wall adherence. However, the odour is a little worse with n-heptane and blends than that of diesel fuel due to overleaning of the mixture. Also, formaldehyde (HCHO) and total hydrocarbon (THC) in the exhaust increase with increasing n-heptane content. The n-decane was tested as a fuel with a high cetane number that can improve ignition delay, which has a direct effect on wall adherence and overleaning. However, with n-decane and blends, the odour rating is about 0.5-1 point lower than for diesel fuel. Moreover, the aldehydes and THC are significantly reduced. This is due to less wall adherence and proper mixture formation.

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