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Gas Power Cycles
Published in Kavati Venkateswarlu, Engineering Thermodynamics, 2020
HCCI strategy proves to be a viable alternative for reducing both nitrogen oxides (NOx) and soot emissions simultaneously without compromising the efficiency. HCCI combines the working principles of both spark ignition (SI) and compression ignition (CI) engines. It takes the advantage of the homogeneous mixture preparation like an SI engine and the combustion like a CI engine and hence is a hybrid between both SI and CI engines. HCCI is described as the one in which the fuel and air are mixed before combustion starts and the mixture auto-ignites as a result of the temperature increase in the compression stroke. It is therefore similar to SI in the sense that both engines use premixed charge and similar to CI as both rely on auto-ignition to initiate combustion.
Bringing the Fire
Published in Patrick Hossay, Automotive Innovation, 2019
A key to making this work is in the fuel. In HCCI, all fuel has to fully vaporize prior to the reaction, or remaining liquid droplets will lead to undesirable emissions. Even more importantly, fuel characteristics are critical to ignition timing in HCCI, since the system relies on spontaneous autoignition, without the timing assistance of either a spark plug or a timed injector. So, in HCCI fuel chemistry plays a determinant role. Since the charge is definitively uniform, variations in fuel mixture or vaporization distribution that shaped spark ignition engines do not exist. As you might guess, typical pump gasoline is generally not precise enough for such a system. The imprecise autoignition point of pump gas makes it hard to achieve a predictable ignition, particularly at low load. Instead, a precisely engineered fuel with a well-defined octane rating is needed. All of this means HCCI needs very accurate control. And HCCI experiments in the laboratory, where control is relatively easy, have at times lead to more CO and more unburned fuel in the emissions.18 A turbocharger, which we will discuss in the next chapter, can help produce more complete combustion by providing more air to the combustion chamber to help ensure that all the fuel is completely burned. But, ensuring a complete and controlled HCCI burn remains a challenge.19
Numerical Study of Equivalence Ratio and Swirl Effect on the Performance and Emissions of an HCCI Engine
Published in C. S. P. Rao, G. Amba Prasad Rao, N. Selvaraj, P. S. C. Bose, V. P. Chandramohan, Mechanical Engineering for Sustainable Development, 2019
T. Karthikeya Sharma, Dhanraj Savary Nasan, G. Amba Prasad Rao, K. Madhu Murthy
Internal combustion (IC) engines have become indispensable prime movers over the past one and half century. Though the performance of conventional spark ignition (SI) and compression ignition (CI) engines is satisfactory, SI engine suffers from poor part load efficiency and high CO emissions. The CI engine yields high particulate and NOx emissions. These effects may be attributed to their conventional combustion process. Of late, a hybrid combustion process called homogeneous charge compression ignition (HCCI) equipped with advanced low-temperature combustion technology is gaining attention by researchers. In principle, HCCI involves the volumetric auto combustion of a premixed fuel, air, and diluents at low to moderate temperatures and at high compression ratios. The other associated advantages with HCCI mode of combustion have been well documented and presented as a potentially promising combustion mode for internal combustion engines.1–3
Effect of turbulence and multiple injection strategies on homogeneous charge compression ignition (HCCI) diesel engines – a review
Published in International Journal of Ambient Energy, 2022
Kavati Venkateswarlu, Konijeti Ramakrishna
HCCI engines can be operated with a wide variety of fuels such as n-butanol, n-heptane, hydrogen, di-methyl ether (DME), di-ethyl ether (DEE) and blends of biodiesel apart from diesel. They can also be operated in dual-fuel mode; however, there is a need of partially premixed fuel for the formation of homogeneous mixture. HCCI engines with the above fuels have been tested both experimentally and numerically. Shahangian et al. (2008) studied numerically the performance of HCCI engine with the effects of intake temperature, pressure and EGR using DME and n-heptane fuels. They showed that DME fuel results in 4 bars indicated mean effective pressure (IMEP) at an intake charge temperature to 65°C and 30% EGR whereas with n-heptane, the same IMEP can be achieved with 30% EGR, 0.39 equivalence ratio and elevated temperature of 97°C. Bedoya et al. (2013) found from their numerical analysis of a four cylinder, 1.9 L Volkswagen turbocharged direct injection (TDI) diesel engine that biogas-HCCI combustion resulted in higher IMEP (about 8 bar), higher indicated efficiency (about 45%) and reduced NOx emissions (0.27 g/kWh). HCCI combustion required an inlet absolute pressure and temperature of 2 bar and 200°C, respectively, which will allow HCCI combustion when biogas is used as a fuel.
Numerical investigation of combustion characteristics of a single-cylinder linear engine fueled by natural gas under the influence of exhaust gas recirculation
Published in International Journal of Ambient Energy, 2022
Mohammad Alrbai, Matthew Robinson, Nigel Clark, Hassan S. Hayajneh
HCCI engines produce ultra-low emission levels and close to zero soot emissions. It has higher efficiencies compared to what is obtained by the conventional spark and the compression ignition (Bui et al. 2021; Murugesan et al. 2021). Many reasons gave this ability to the HCCI combustion like the nature of the multi-spot unconstrained combustion that encountered within the HCCI combustion. This is because of the lean and well-mixed fuel–air mixture that delivers a high heat release rate (HRR) and relatively short flame propagation. Another reason is the higher compression ratio values that can be utilised from the HCCI engines which yield to higher thermal efficiencies (Alrbai and Qawasmeh 2018; Parthasarathy et al. 2020). However, the need for the right control of the ignition time and the lack of ability to accomplish high engine loads are among the limitations of HCCI engines (Alrbai, Robinson, and Clark 2020; Polat et al. 2020).
Enhancement of mixture homogeneity for DI-CI engine to achieve Homogeneous Charge Compression Ignition (HCCI) combustion characteristics: a numerical approach
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Kattela SivaPrasad, Surapaneni Srinivasa Rao, Vysyaraju Rajesh Khana Raju
In the transportation and power generating sectors, compression ignition (CI) engines are more widespread. However, the engine are producing higher emissions (such as NOx and soot) and not meeting emissions regulations (Kattela et al. 2019). In order to decrease the emissions and maintain the better fuel economy, the researchers are searching new combustion technology. HCCI combustion technology is capable to decrease the soot and NOx emissions significantly (Bendu and Murugan 2014; Mofijur et al. 2019). HCCI is a form of combustion in which a homogeneous mixture of fuel and air is created and burned inside the combustion chamber by creating an auto ignition situation. HCCI works on the principle of both SI (spark ignition) and CI engine in the sense that a mixture of the charge (fuel and air) is prepared as that of SI engine and compression ignited as in CI engine (Hasan and Rahman 2016). HCCI combustion is much more efficient and thus leads to a lot of fuel saving and reduces the lot of NOx and soot emission (Saxena and Bedoya 2013). To achieve such combustion, HCCI needs a high level of control over combustion timing and rate of combustion HCCI combustion mode can achieve using different strategies such as varying the injection timing, multiple injection strategies, EGR, different operating and design parameters (CR, intake pressure, FIP, swirl ratio, and piston bowl, etc.) (Yao, Zheng, and Liu 2009). Varying the single parameter cannot achieve HCCI mode. Hence, multiple parameter studies are required to enabling the HCCI characteristics.