Selection and thermodynamic analysis of a turbocharger for a producer gas-fuelled multi-cylinder engine

Abstract

The current work addresses the use of producer gas, a bio-derived gaseous alternative fuel, in engines designed for natural gas, derived from diesel engine frames. Impact of the use of producer gas on the general engine performance with specific focus on turbo-charging is addressed. The operation of a particular engine frame with diesel, natural gas and producer gas indicates that the peak load achieved is highest with diesel fuel (in compression ignition mode) followed by natural gas and producer gas (both in spark ignite mode). Detailed analysis of the engine power de-rating on fuelling with natural gas and producer gas indicates that the change in compression ratio (migration from compression to spark ignited mode), difference in mixture calorific value and turbocharger mismatch are the primary contributing factors. The largest de-rating occurs due to turbocharger mismatch. Turbocharger selection and optimization is identified as the strategy to recover the non-thermodynamic power loss, identified as the recovery potential (the loss due to mixture calorific value and turbocharger mismatch) on operating the engine with a fuel different from the base fuel. A turbocharged after-cooled six cylinder, 5.9 l, 90 kWe (diesel rating) engine (12.2 bar BMEP) is available commercially as a naturally aspirated natural gas engine delivering a peak load of 44.0 kWe (6.0 bar BMEP). The engine delivers a load of 27.3 kWe with producer gas under naturally aspirated mode. On charge boosting the engine with a turbocharger similar in configuration to the diesel engine turbocharger, the peak load delivered with producer gas is 36 kWe (4.8 bar BMEP) indicating a de-rating of about 60% over the baseline diesel mode. Estimation of knock limited peak load for producer gas-fuelled operation on the engine frame using a Wiebe function-based zero-dimensional code indicates a knock limited peak load of 76 kWe, indicating the potential to recover about 40 kWe. As a part of the recovery strategy, optimizing the ignition timing for maximum brake torque based on both spark sweep tests and established combustion descriptors and engine-turbocharger matching for producer gas-fuelled operation resulted in a knock limited peak load of 72.8 kWe (9.9 bar BMEP) at a compressor pressure ratio of 2.30. The de-rating of about 17.0 kWe compared to diesel rating is attributed to the reduction in compression ratio. With load recovery, the specific biomass consumption reduces from 1.2 kg/kWh to 1.0 kg/kWh, an improvement of over 16% while the engine thermal efficiency increases from 28% to 32%. The thermodynamic analysis of the compressor and the turbine indicates an isentropic efficiency of 74.5% and 73%, respectively.

Influence of fuel hydrogen fraction on syngas fueled SI engine: Fuel thermo-physical property analysis and in-cylinder experimental investigations

“…This assessment is based on previous experience with PG fueled operation wherein it has been observed that under naturally aspirated and stoichiometric operation, the peak load delivered by the engine is limited to about 4.65 kWe per litre of swept volume. The factors contributing to power derating and the corresponding recovery options have been discussed by Dasappa [43] and the authors [27] elsewhere.…”

“…The highest calorific value at 2.41 MJ/kg is however lower than NG calorific value of 2.5 MJ/kg (conservative estimate based on 45 MJ/kg fuel calorific value and 17:1 air to fuel ratio). The reduced mixture energy density coupled with lower CR results in engine power de-rating [27,43]. Hydrogen with high thermal conductivity/diffusivity adds significantly to the mixture conductivity/diffusivity, potentially enhancing the convective heat losses from the engine.…”

Development and Testing of a Laboratory Scale Induction System for a Bottled Producer Gas Fuelled IC Engines

“…Producer gas (PG) is one such renewable fuel [2] which can meet this twin requirement of being renewable and carbon neutral via biomass gasification technology [3]. According to literature, a typical biomass based power generation would reduce approximately 30 % CO 2 emissions annually as compared to coal fired thermal power plant [4]. Literature reveals that in Europe about one million engines were powered via gasifiers during World War-II and the technology soon disappeared due to easy availability of baseline (fossil) liquid fuels [5].…”

Numerical and experimental analysis on the effects of turbocharged compressed bio-methane-fueled automotive spark-ignition engine

“…This has led the automotive manufacturer to introduce downsizing concepts that optimize a suitable compression ratio necessary for turbocharging. Recent developments have been made in NA engines for which design parameters at higher compression ratio are brought equivalent to a lower compression engine by means downsizing technique which usually accommodates a turbocharger, this offers enhanced charge cooling, knock free operation, and effective scavenging of the residual gases to improve the low-end torque (Shivapuji and Dasappa 2014), (Padmavathi R, Nandhakumar K 2010). The mass and energy transfer becomes essential parameters that determine a turbocharger's performance, which is necessary for matching.…”