Reduced Compression Ratio Research Articles

Comparison of methods for diagnosing marine IC engines based on working medium parameters including exhaust gas specific enthalpy

Article points out methods currently used to diagnose marine engines in operation. The development of tools and programs for implementing these methods was pointed out. The problem of unsatisfactory measurement susceptibility of marine engines was highlighted. Three methods of parametric diagnosis are presented: measurement of in-cylinder parameters and in exhaust gas duct, numerical simulation due to computer software and calculations based on Wibe function. Unfitness states that were analyzed during tests are presented: reduced injection pressure, obstructed intake air duct and reduced compression ratio. The specific enthalpy of the exhaust gas within one engine cycle was determined as a new diagnostic parameter. As a supplement, thermograms of the engine in various states of inoperability were presented. The obtained results were compared and a series of conclusions derived from them were presented. It was evaluated that numerical simulation is an excellent tool for planning experimental studies. Tests on the engine in operation were found to be the most diagnostically reliable.

Investigation on NOx control of a CI engine through the collective effect of hydrogen and biodiesel blend at modified compression ratio

The main challenges with using biodiesel in CI engines are higher NOx emissions and reduced brake thermal efficiency. These biodiesel-related issues can be handled by concurrently introducing gaseous fuels along with primary fuel into CI engines. This study examines the effects of hydrogen in a dual fuel mode operation with diesel and Calophyllum inophyllum biodiesel blend (B20) at different compression ratios on the engine's performance, combustion, and emission characteristics. A single-cylinder, 4-stroke, variable compression ratio engine operating at 1500 rpm was used for the research. A standard compression ratio (SCR) of 17.5 and a modified compression ratio (MCR) of 15.5 at a constant hydrogen flow rate of 6 L per minute (lpm) were used with diesel and B 20. The addition of hydrogen with diesel and B20 resulted in higher cylinder pressure and heat release rate when compared to pure diesel and B20 operation. This resulted in a shorter delay period (by an average of 9.4 % and 7.1 %) with lower peak pressure than pure diesel and B20 operation. During the dual fuel mode of H2 with B 20 at a modified compression ratio, the maximum heat release rate was decreased and its occurrence was retarded. NOx, UBHC, and CO emissions of the engine were decreased significantly by an average of 20.8% 43.7, %, and 22 % respectively with 37.7 % increase in smoke opacity. The increase in NOx emission with the use of H2 with diesel was reduced by operating H2 with B20 and at a reduced compression ratio. This lower emission was achieved with a compromise of a marginal decrease in engine brake thermal efficiency.

Experimental analysis of the effect of hydrogen as the main fuel on the performance and emissions of a modified compression ignition engine with water injection and compression ratio reduction

This study aimed to investigate the combined effects of compression ratio (CR), start of injection angle (SOI) and water injection (WI) on the performance, including NOx emissions, of a modified turbocharged compression ignition engine using H2 as the primary fuel and diesel solely as a pilot ignition source. WI and H2 were both injected into the intake manifold just after the charge heat exchanger. Test conditions varied the engine speed from 1500 rpm to 2750 rpm, covering a wide range of the original engine's operating conditions, water mass flow varied from 0 to 0.795 g/cycle and SOI for pilot ignition was studied in the range 10°, 5°, 0° before top dead center. Subsequently, the study examined the combined effect of reducing the engine's CR from 17.5:1 (base) to 13.5:1, in one-point increments, reducing SOI and water addition to further enhance the hydrogen energy share (HES).HES varied from 0 % to 85 % under different engine conditions, and WI and SOI were employed to prevent knocking and ensure that the maximum combustion pressure did not exceed 160 bar. The test results indicate that NOx emissions increase with HES, but reducing the CR results in a reduction in NOx emissions of approximately 50 %. Additionally, WI further reduces NOx emissions by up to 50 %. The experimental evidence demonstrates that combining WI with CR and SOI reduction can effectively lower NOx emissions, achieving an efficiency greater than 35 % and therefore approaching the base diesel mode's efficiency. This also reduces the maximum in-cylinder pressure, allowing for an increase in turbocharger pressure and consequently enhancing the engine's specific power. The maximum engine power achieved was 31.6 kW at 2500 rpm (mean effective pressure of 10.1 bar), with a CR of 15.5, SOI at 10°, 1.5 kg/kWh of water, a HES of 81 %, and a minimum NOx level of approximately 480 ppm, with a maximum combustion pressure below 120 bar.

High-Pressure Calibration TiN Equation of State

High pressure is becoming an interesting area of research for originating vital properties in crystalline solids. In the present study, the pressure equation of the state of TiN was investigated by employing various equations of state (EoS) presented in the literature, such as Dodson EoS, Barden EOS, Birch-Murnaghan (B-M) EoS. The EoSs were processed to find the high-pressure effects on the characterizations of TiN such as volume compression ratio, bulk modulus B, Grüneisen parameter, and phonon frequency spectrum. It was shown that a gigantic pressure results in a significant reduction in the volume of the TiN material, and the volume compression ratio reduction, is almost the same for the existing equations of state and the comparative literature results up to a pressure of 80 GPa. The maximum pressure difference is observed to be 4.85 GPa. over the entire pressure of 120GPa. Increasing the bulk modulus with high pressure was expected by the present EoSs, and up to the pressure of about 60 GPa, all curves of bulk modulus are matched with each other. Eventually, a fair comparison has been made between the present results and the first principle approximation along with the generalized gradient approximation method in which a perfect agreement was observed. Finally, the feasibility of TiN EoS as a standard pressure calibration was demonstrated.

Performance evaluation of Kipevu-III 120 MW power station and conversion to dual-fuel power plant

Diesel power plants use diesel engines as prime movers powered mainly by heavy fuel oil or industrial diesel oil and with potential for conversion to gas engines or dual fuel engines. The global concerns over prices of diesel and heavy fuel oil and energy related greenhouse gas emissions have created demand for natural gas as an alternative fuel for power generation by diesel power stations. This study involved a performance analysis of an operating diesel power plant and its potential conversion to dual fuel engine power plant. Dual fuel engines have reduced fuel costs and greenhouse gas emissions since natural gas is the cleanest fossil fuel. For a conventional diesel engine to run on diesel, the fuel injection system is modified to handle gas and a mixture of gas and diesel. Other modifications are the introduction of an electronic control unit, reduction in air fuel ratio, installation of a fuel mixer, and reduction of compression ratio. The conversion requires provision for natural gas storage facilities and supply system which were introduced in the proposed design modification. The study showed that dual fuel engine power plants have better performance indicators like lower specific fuel consumption, higher indicated and brake thermal efficiency, cheaper power produced, less emissions per unit power and thus reduced environmental impact. Conversion to dual fuel engines will reduce the cost of electricity generation, reduce emissions particularly Sulphur dioxide while accommodating fuel flexibility like use of biofuel to substitute diesel.

Effects of piston shape and nozzle specifications on part-load operation of natural gas–diesel dual-fuel RCCI engine and its application to high load extension

• Effects of piston shape and multi-angle nozzle were evaluated for DF RCCI operation. • Enhanced air utilization w/multi-angle nozzle reduced combustion and HT losses. • The highest GIE of RCCI improved as 51.8 % by hardware modifications. • Intake air amount could be increased by lowering CR (from 17 to 15) at the maximum load. • The maximum load of RCCI could be extended from 81 (reference) to 101 kW of BP. In this study, the effects of modifications of both the piston shape and injector nozzle are experimentally investigated for high load extension of a natural gas–diesel dual-fuel reactivity-controlled compression ignition (RCCI) engine. First, a bathtub shape with a reduced compression ratio is applied to the modified piston which was reported to improve the flame propagation in squish volume, the cooling loss, and the air induction rate under the same limit of in-cylinder pressure from previous studies. In addition, a multiangle two-layer injector is used to extend the maximum load, which has been proven to be effective for unburned hydrocarbon emissions and gross indicated efficiency in part-load operation in our previous study. The experiments are conducted under both 1200 rpm part-load operation (approximately 1950 J/cylinder per cycle of fuel input energy) and 1800 rpm maximum load operation. The objectives are to comprehensively evaluate the effects of the modifications on natural gas–diesel RCCI operation and verify the effects of all load conditions. The experimental results reveal that the changes in the piston—reduction in the compression ratio and a bathtub piston shape—are effective for both NOx and smoke emissions as the diesel injection timing is advanced. Although the multi-hole double layer (combined narrow and wide injection) has less effect on emissions compared to that of the change in piston, it affects the mixing process inside the cylinder, thus retarding the combustion phasing, prolonging the combustion duration, and eventually reducing the cooling loss. Both modifications are highly effective for advanced diesel injection timing corresponding to RCCI operation, which extends high-load operation from 80.9 to 101 kW of brake power, relatively 24.8 % increase, by adopting both the piston and injector modifications. Based on the modifications, the mass fraction of natural gas is suggested to be approximately 80 %. A higher fraction causes the variation in the maximum in-cylinder pressure to be extremely sensitive to allow robust operation. In contrast, if it is lower, the amounts of both NOx and smoke emissions exceed the emission standard levels (0.4 g/kWh and 15 mg/kWh for NOx and smoke emissions, respectively, corresponding to Stage-V of non-road engine operation).

Study of the effects of trapped compression ratio on the heavy fuel operation of a spark ignition unmanned aerial vehicle engine

PurposeThis paper aims to present experimental experience of heavy fuelling of a spark ignition crankcase scavenged two-stroke cycle unmanned aerial vehicle (UAV) engine, particularly focusing on the effects of compression ratio variation, and to cross-correlate with the results of fluid dynamic modelling of the engine and fuels used.Design/methodology/approachOne-dimensional modelling of the engine has been conducted using WAVE software supported by experimental dynamometer testing of a spark ignition UAV engine to construct a validated computational model using gasoline and kerosene JET A-1 fuels.FindingsThe investigation into the effects of compression ratio variation via fluid dynamic simulation and experimental testing has allowed an assessment of the approach for improving heavy fuel operation of UAV engines using auxiliary transfer port fuel injection. The power level achieved with reduced compression ratio heavy fuel operation is equal to 15.35 kW at 6,500 revolutions per minute compared to 16.27 kW from the standard gasoline engine or a reduction of 5.7%.Practical implicationsThe studied engine is specifically designed for UAV applications. The validation of the computational models to explore the effects of compression ratio and heavy fuel injection on the solution and cost is supported by experimental tests.Originality/valueThe application of auxiliary port fuel injection of heavy fuel and associated compression ratio optimisation offers an alternative approach to achieve the safety and logistical challenges of the single fuel policy for UAVs. The application of WAVE to simulate crankcase scavenged two-stroke cycle engines has been applied in very few cases. This study shows further exploratory work in that context.

Numerical study on knock characteristics and mechanism of a heavy duty natural gas/diesel RCCI engine

In this paper, the knock phenomenon of reactivity controlled compression ignition (RCCI) engine fueled with natural gas/diesel was numerically studied. The knock mechanism of the RCCI engine is explained and the strategy of suppressing knock is put forward. The knock characteristics were studied by setting monitoring points in different spaces positions of the cylinder. The results show that the pressure oscillation amplitude at the center and edge of the cylinder is large under the high load condition of RCCI engine. In addition, the knock mechanism was studied by using pressure difference method, maximum amplitude of pressure oscillation, important components, temperature isosurface, pressure fluctuation and heat release rate. The results show that the knock of RCCI engine is mainly caused by the end-gas auto-ignition. The pressure difference results show that the characteristic frequency is consistent with the natural resonance mode (0,1) of the cylindrical combustion chamber. On this basis, the effects of pilot oil injection timing and compression ratio on engine knock are further studied. It is confirmed that diesel knock and end-gas knock may exist simultaneously in the same cycle when RCCI engine knock occurs. And diesel knock occurs before top dead center, and end-gas knock occurs after top dead center. Proper adjustment of pilot oil injection timing and reduction of compression ratio can effectively suppress engine knock.

MobilePrune: Neural Network Compression via ℓ0 Sparse Group Lasso on the Mobile System.

It is hard to directly deploy deep learning models on today’s smartphones due to the substantial computational costs introduced by millions of parameters. To compress the model, we develop an -based sparse group lasso model called MobilePrune which can generate extremely compact neural network models for both desktop and mobile platforms. We adopt group lasso penalty to enforce sparsity at the group level to benefit General Matrix Multiply (GEMM) and develop the very first algorithm that can optimize the norm in an exact manner and achieve the global convergence guarantee in the deep learning context. MobilePrune also allows complicated group structures to be applied on the group penalty (i.e., trees and overlapping groups) to suit DNN models with more complex architectures. Empirically, we observe the substantial reduction of compression ratio and computational costs for various popular deep learning models on multiple benchmark datasets compared to the state-of-the-art methods. More importantly, the compression models are deployed on the android system to confirm that our approach is able to achieve less response delay and battery consumption on mobile phones.

Experimental Investigations on Enhancement of DME Energy Shares in Compression-Ignition Engine Under Dual Fuel Mode Using Reduced Compression Ratio

The effects of the compression ratio (CR), which was reduced from base (19:1) to (17:1), on the enhancement of Dimethyl Ether Energy Share (DME ES) and emissions reduction in a 5.5 kW DICI (direct injection compression ignition) engine are studied. The experimental tests were conducted on the engine with DME as main fuel and diesel as pilot fuel at 13 Nm torque and speed of 2200 rpm condition under dual fuel mode (DME-diesel). The maximum DME energy share (DME ES) enhanced drastically from 44% with base CR to 53% with the reduced CR. Smoke emission decreased to nearly zero levels with both CRs (19:1 and 17:1). CO and HC emissions significantly decreased with 53% of DME ES with reduced CR. NOx emission decreased drastically with the reduced CR (17:1). However, brake thermal efficiency is marginally droped with the reduced compression ratio. The combustion characteristics are discussed in detail.

Experimental Studies of Low-Load Limit in a Stoichiometric Micro-Pilot Diesel Natural Gas Engine

While operating at light loads, diesel pilot-ignited natural gas engines with lean premixed natural gas suffer from poor combustion efficiency and high methane emissions. This work investigates the limits of low-load operation for a micro-pilot diesel natural gas engine that uses a stoichiometric mixture to enable methane and nitrogen oxide emission control. By optimizing engine hardware, operating conditions, and injection strategies, this study focused on defining the lowest achievable load while maintaining a stoichiometric equivalence ratio and with acceptable combustion stability. A multi-cylinder diesel 6.7 L engine was converted to run natural gas premix with a maximum diesel micro-pilot contribution of 10%. With a base diesel compression ratio of 17.3:1, the intake manifold pressure limit was 80 kPa(absolute). At a reduced compression ratio of 15:1, this limit increased to 85 kPa, raising the minimum stable load. Retarding the combustion phasing, typically used in spark-ignition engines to achieve lower loads, was also tested but found to be limited by degraded diesel ignition at later timings. Reducing the pilot injection pressure improved combustion stability, as did increasing pilot quantity at the cost of lower substitution ratios. The lean operation further reduced load but increased NOx and hydrocarbon emissions. At loads below the practical dual-fuel limit, a transition to lean diesel operation will likely be required with corresponding implications for the aftertreatment system.

Quantum Otto engines at relativistic energies

Relativistic quantum systems exhibit unique features not present at lower energies, such as the existence of both particles and antiparticles, and restrictions placed on the system dynamics due to the light cone. In order to understand what impact these relativistic phenomena have on the performance of quantum thermal machines we analyze a quantum Otto engine with a working medium of a relativistic particle in an oscillator potential evolving under Dirac or Klein–Gordon dynamics. We examine both the low-temperature, non-relativistic and high-temperature, relativistic limits of the dynamics and find that the relativistic engine operates with higher work output, but an effectively reduced compression ratio, leading to significantly smaller efficiency than its non-relativistic counterpart. Using the framework of endoreversible thermodynamics we determine the efficiency at maximum power of the relativistic engine, and find it to be equivalent to the Curzon–Ahlborn efficiency.

Experimental study of wall-impinging diesel spray ignition and combustion characteristics under critical conditions

The ignition stability of diesel engines during cold starting is a key issue limiting the further reduction of compression ratio. To investigate the effect of diesel spray and wall interaction on ignition stability at the critical conditions with a low ambient density and different ambient temperatures, the spray characteristics, ignition process, and flame propagation process were quantitatively analyzed using the Mie-scattering and shadowgraph method, and direct photography method of simultaneous photography based on a constant volume combustion chamber. It was discovered that the spray penetration length spray cone angle, spread radius, and vapor-phase floatation height were insensitive to ambient temperature, but liquid-phase floatation height decreased as the ambient temperature increased. Ignition delay time decreased as the ambient temperature increased, but ignition positions all occurred near the wall surface and far from the axis of the nozzle. However, the distance between ignition position and axis of nozzle, and the distance between ignition position and wall both decreased as the ambient temperature increased. Higher equivalent ratio zones are more susceptible to low temperature reaction than lower equivalent ratio zones. However, the threshold for high temperature reaction of higher equivalent zones was higher than that of lower equivalent ratio zones. Yellow flames were usually accompanied by the production of a blue flame around them, and blue flame propagates faster than yellow flame under critical conditions.

Randomized Low-Rank Approximation Based Massive MIMO CSI Compression

Massive multiple-input multiple-output (MIMO) is regarded as one enabling technique to improve channel capacity and energy/spectrum efficiency of 5G communications. To attain such potential benefits, accurate channel information is critical to the transmitter, which yet remains a challenging task for frequency division duplexing (FDD) systems, i.e., the channel state information (CSI) feedback tends to be resource-demanding especially for massive MIMO communications. In this work, we propose a novel CSI feedback method with low complexity and high precision, which is inspired by randomized matrix approximation. Our approach exploits the inherent low-rank characteristic of a large channel matrix, and approximates it by small sub-matrices which are then reported to transmitter to recover a CSI matrix. Theoretical bounds of the recovered CSI in both error-free and error cases are derived. Simulation results demonstrate our method could recover CSI accurately via an extremely low complexity and yet achieve a largely reduced compression ratio (or feedback overhead), compared to other schemes. It thus has the great potential in the emerging massive MIMO FDD communications.

Particle acceleration and non-thermal emission in colliding-wind binary systems

ABSTRACT We present a model for the creation of non-thermal particles via diffusive shock acceleration in a colliding-wind binary. Our model accounts for the oblique nature of the global shocks bounding the wind–wind collision region and the finite velocity of the scattering centres to the gas. It also includes magnetic field amplification by the cosmic ray induced streaming instability and the dynamical back reaction of the amplified field. We assume that the injection of the ions and electrons is independent of the shock obliquity and that the scattering centres move relative to the fluid at the Alfvén velocity (resulting in steeper non-thermal particle distributions). We find that the Mach number, Alfvénic Mach number, and transverse field strength vary strongly along and between the shocks, resulting in significant and non-linear variations in the particle acceleration efficiency and shock nature (turbulent versus non-turbulent). We find much reduced compression ratios at the oblique shocks in most of our models compared to our earlier work, though total gas compression ratios that exceed 20 can still be obtained in certain situations. We also investigate the dependence of the non-thermal emission on the stellar separation and determine when emission from secondary electrons becomes important. We finish by applying our model to WR 146, one of the brightest colliding wind binaries in the radio band. We are able to match the observed radio emission and find that roughly 30 per cent of the wind power at the shocks is channelled into non-thermal particles.

Design and Development of a Hardware Efficient Image Compression Improvement Framework

Background: In the region of image processing, a varied number of methods have already initiated the concept of data sciences optimization, in which, numerous global researchers have put their efforts upon the reduction of compression ratio and increment of PSNR. Additionally, the efforts have also separated into hardware and processing sections, that would help in emerging more prospective outcomes from the research. In this particular paper, a mystical concept for the image segmentation has been developed that helps in splitting the image into two different halves’, which is further termed as the atomic image. In-depth, the separations were done on the bases of even and odd pixels present within the size of the original image in the spatial domain. Furthermore, by splitting the original image into an atomic image will reflect an efficient result in experimental data. Additionally, the time for compression and decompression of the original image with both Quadtree and Huffman is also processed to receive the higher results observed in the result section. The superiority of the proposed schemes is further described upon the comparison basis of performances through the conventional Quadtree decomposition process. Objective: The objective of this present work is to find out the minimum resources required to reconstruct the image after compression. Method: The popular method of quadtree decomposition with Huffman encoding used for image compression. Results: The proposed algorithm was implemented on six types of images and got maximum PSNR of 30.12dB for Lena Image and a maximum compression ratio of 25.96 for MRI image. Conclusion: Different types of images are tested and a high compression ratio with acceptable PSNR was obtained.

An efficient framework for increasing image quality using DRN Bi-layer enfolded compressor

Lossy /lossless image compression technique results will either improve the quality of image with reduced compression ratio or degrades the image with better compression ratio. But on dealing with the combined lossy/lossless techniques, they provide the output with better image quality and high compression rate, however, the techniques failed to obtain better efficiency due to less predictive nature. Hence, to acquire an image having better compression rate with improved predictive nature, a novel framework is introduced in our proposed work. It uses a Deep Residual Network Bi-Layer Enfolded Compressor (DRN-BLEC) to enhance the image quality. In order to obtain better compression rate, the Mexican Meyer Hat Wavelet Transform (MMHWT) is used. Similarly, the well knowledge quantization is achieved by utilizing DRN for learning; it is then followed by the Lloyds quantization technique that groups the feature values by quantizing it, which in turn boost-up the resolution of the image. Consequently with DRN, the process of encoding and decoding doesn’t requires to be done separately since two residual layer of the DRN are trained to encode and decode the images, which thereby reduces the time required for compression process. Thus a compressed image with high resolution is obtained without redundancy, moreover with high compression ratio. The architecture of the DRN-BLEC is implemented in MATLAB and the respective result structure is validated.

Worst Case Driven Display Frame Compression for Energy-Efficient Ultra-HD Display Processing

Display frame compression is an effective technique to address the challenge of external memory access in ultrahigh definition video display system. Nevertheless, previously proposed display frame compression designs are inadequate in terms of either energy efficiency or throughput. This paper aims to exploit the algorithm and very large scale integration (VLSI) architecture of a worst case driven display frame compression. By using a prediction-and-compression framework and a semi-fixed length coding scheme, the proposed design can achieve the much better balance between compression efficiency and throughput, and substantially reduce the bandwidth requirement and energy consumption of external memory system in the meanwhile. Extensive experiments demonstrate that the proposed display frame compression achieves 5.7-dB peak signal-to-noise ratio improvement, 3.1% compression ratio reduction, 3 × throughput, and 66.4% hardware cost saving, compared with the best previous work. In addition, the proposed VLSI design can support the throughput of 4 K × 2 K@60 Hz and reduce at least 17.6% energy consumption of external memory system by exploiting dynamic voltage and frequency scaling, compared with conventional display frame compression works.

Experimental optimization of reactivity controlled compression ignition combustion in a light duty diesel engine

Reactivity Controlled Compression Ignition (RCCI) is emerging as a most promising combustion strategy to achieve near zero oxides of nitrogen (NOx) and smoke emissions along with higher brake thermal efficiency. The present work attempts to implement RCCI strategy in a production, light duty diesel engine by replacing an existing mechanical fuel injection with a flexible common rail direct injection diesel system and a low pressure gasoline port fuel injection system. Further, the engine compression ratio is reduced through modifications in piston bowl. Using a suitable controller, the engine operating parameters in terms of direct injected diesel timings, injection pressure, port injected gasoline quantity and gasoline to diesel ratio at each load conditions are optimized to achieve maximum brake thermal efficiency. Before modifications, the engine is run under conventional combustion mode at rated speed, varying loads to establish baseline reference data. The obtained results show that the engine could be operated in RCCI mode over its entire load range with a maximum increase of 14.2% brake thermal efficiency, near zero NOx and smoke emissions compared to conventional combustion. Further, reducing compression ratio is found to increase brake thermal efficiency by 7.6% and reduce carbon monoxide by 16.8% in RCCI.

Application of dual-fuel combustion over the full operating map in a heavy-duty multi-cylinder engine with reduced compression ratio and diesel oxidation catalyst

This research focuses on the potential of the dual-fuel combustion engine fueled with regular gasoline and diesel to meet the Euro V emission standard over the whole operating range with a simple after-treatment system. For this purpose, a mode-switching strategy was investigated in this work. The engine maps of this strategy were obtained using a dedicated experimental procedure on a modified heavy-duty multi-cylinder engine. The switching of dual-fuel modes mainly depended on the engine load. At 25% engine load, fully premixed reactivity controlled compression ignition combustion was applied to achieve high efficiency and low emission combustion. At operating conditions higher than 50% load, homogeneous charge induced ignition combustion with up to three diesel injections (pre-, main and post-injections) was applied. Then, the effects of compression ratio on the dual-fuel combustion over the full operating map were explored and analyzed in detail. It was found that in spite of a slight increase in the fuel consumption, better combustion and emission performance over the whole operating map could be achieved in the dual-fuel combustion with a lower compression ratio. Finally, the effects of diesel oxidation catalyst were also investigated. The exhaust temperatures of this dual-fuel strategy were higher than the diesel oxidation catalyst light-off temperature, ensuring an effective conversion of the total hydrocarbon and carbon monoxide emissions. Furthermore, from the particle number-size distribution analysis, it was found that reactivity controlled compression ignition was dominated by the nucleation mode particles, while homogeneous charge induced ignition was dominated by the accumulation mode particles which tended to increase as the load increased. In addition, with a lower compression ratio of 16:1 and the application of diesel oxidation catalyst, the cycle-averaged regular emissions of the mode-switching combustion strategy could meet the Euro V emission standard simultaneously in the European Stationary Cycle test.