Diesel Engine Research Articles

A comparative study of mono ethylene glycol economic production via different techniques

AbstractMono-ethylene glycol (MEG) is a high-volume chemical intermediate used as a raw material for a variety of chemical products. It could also be used as a hydrate inhibitor in natural gas. Recently, the importance of MEG has been increased due to its usage as a supporting emulsifier in diesel engines to reduce NOx and soot emissions, in addition to its usage as an additive to dual fuel diesel engines. The increase consumption of MEG in wide range of applications leads to the search for the most efficient, environmental friendly and cost effective technique to produce more quantities of it. MEG is most commonly manufactured via the hydration of ethylene oxide (EO). In this work, two different technologies of EO hydration to produce MEG are compared; the direct hydration of EO with water and the indirect hydration through the usage of ethylene carbonate (EC) as an intermediate. Comparative economic and environmental impact assessments were performed based on plant-scale simulations (per 600,000 tons per year of MEG produced) of the two hydration technologies using Aspen HYSYS version 11 simulation software. Economic analysis showed that the utilities’ energy consumption for direct hydration process is significantly higher than for indirect hydration by 279 megawatts. On the other hand, the environmental impact assessments showed that GHG emissions from natural gas power generation from utilities from direct hydration are three times greater than GHG emissions from indirect hydration. This leads to indirect hydration of ethylene oxide through ethylene carbonate formation being considered economically and environmentally preferable compared to the direct hydration process of ethylene oxide.

Generalized composite multiscale improved diversity entropy and its application to diesel injector fault feature extraction and diagnosis

The diesel injector is the core component of marine diesel engines, and its health monitoring is one of the keys to ensuring the efficient and reliable operation of diesel engines and even ships. However, extracting effective feature information from nonlinear dynamic signals is the difficulty in realizing intelligent fault diagnosis of diesel fuel injectors. The existing diversity entropy (DE) is an advanced algorithm for extracting fault features. Still, it has the problem of failing to obtain sufficiently effective fault features, thus affecting diagnostic accuracy due to its inherent defects. To solve the above problem, a new generalized composite multiscale improved diversity entropy (GCMIDE) is first proposed, and the comparative advantages of the proposed entropy in terms of consistency, robustness, and computational efficiency are verified with common noise-simulated signals. GCMIDE is further utilized as an excellent means of feature extraction, and a new injector fault diagnosis method, GCMIDE-Relieff-SSA-BP, is proposed to meet the needs of efficiency and practicality in fault diagnosis. Finally, the method is adopted for the diagnostic experiments of diesel fuel injectors with different fault types and different fault degrees for full validation. The experimental results all indicate that, in comparison with six commonly used entropy-based fault diagnosis methods, the proposed method has the best feature extraction performance and fault diagnosis accuracy under a different number of features or different training sample ratios. This provides an effective tool for fault diagnosis of injectors and even intelligent operation and maintenance of diesel engines.

An on-road experimental emissions evaluation of a diesel engine fueled with pyrolysis oil from waste plastics, pure and blended with biodiesel-A Mexican case

Pyrolysis of plastic waste generates alternative fuels that are useful for thermal devices. However, it is the subsequent fractionation process that truly distinguishes itself, refining these fuels to a quality comparable to petroleum derivatives such as diesel and gasoline, thereby making them suitable for direct use in internal combustion engines. This study evaluated the effect on emissions of an internal combustion engine fueled with waste plastic oil diesel-like fuel and its blend with biodiesel. The tests were conducted on-road using a typical light-duty diesel vehicle for passenger or courier transportation. Three tests were carried out, the first one with petroleum diesel (D100) as the reference fuel, the second one with waste plastic oil diesel-like fuel (WPO-DL), and the last with a blend of 80% WPO-DL and 20% biodiesel obtained from waste cooking oil (WPO-DL80WCO20). The main findings were a reduction in the generation of NOx when using WPO-DL. However, using WPO-DL increased the production of CO and HC, attributed to the presence of more heavy hydrocarbons compared to that of D100. Additionally, for the WPO-DL80WCO20 blend under acceleration conditions HC decreased under all acceleration conditions. These findings demonstrate that the distilled fuel obtained from the pyrolytic oil product of non-recyclable plastic waste by conventional methods would contribute to the global energy transition and reduce the presence of tons of non-recyclable plastic waste by traditional methods.

Exploring the combustion, emission and performance of n-Butanol with Deccan hemp oil methyl ester on dual fuel diesel engine.

This experiment investigated the feasibility of using n-butanol with Deccan hemp oil methyl ester derived from Hibiscus cannabinus. Deccan hemp oil, from warm countries like India is an eco-friendly alternative energy source since it is reusable and easy to locate. The Acetone-Butanol-Ethanol (ABE) process made the n-butanol. Further, 60% Deccan hemp oil methyl ester and 40% diesel were mixed and injected directly into the engine's cylinders. The engine's performance was evaluated by adding varying quantities of n-butanol (10%, 20%, or 30%) to the intake pipe at various intervals throughout the experiment. The results showed that using pure Deccan hemp oil or its methyl ester was much better for the engine's performance than regular diesel fuel. This was compared to how well the engine worked when diesel was used. However, the engine ran much better when fed a mix of 60% Deccan hemp oil methyl ester and 40% diesel (B60). Even though it couldn't compete with diesel engines in speed, this was still the case. The engine was running in dual fuel mode when n-butanol was added to the mixture. This made the carbon monoxide, unburned hydrocarbons, and smoke outputs go down. All of these decreases happened without making the engine less able to work. NOx emissions from the B60Bu10 (10% n-butanol share), B60Bu20, and B60Bu30 dual fuel combinations went up by 2.65%, 6%, and 8.9%, respectively, at full load, while smoke emissions went down by 18.33%, 23.75%, and 30.83%, in that order. The study's results show that adding Deccan hemp oil methyl ester to diesel fuel and injecting n-butanol into a dual-fuel diesel engine could help lower emissions without affecting the engine's performance.

Impact of nano cerium oxide addition with pyrolysis waste plastic oil on combustion, performance and emission characteristics of CRDI diesel engine

Abstract This investigation examined the effect of incorporating cerium oxide (CeO2) nanoparticle into diesel and waste plastic oil (WPO) blends on the combustion, performance and emission characteristics of the diesel engine. The WPO was extracted from low density polyethylene using plastic pyrolysis. The blending of diesel and WPO with combination of D70:WPO30 and D50:WPO50 was prepared to evaluate the engine operation. Additionally, the spherical sized CeO2 with 50 mg/L and 100 mg/L was added with this blend. The various blends named as Diesel, D-WPO30, D-WPO30+Ce50, D-WPO30+Ce100, D-WPO50, D-WPO50+Ce50 and D-WPO50+Ce100 were used in this investigation to operate the engine under various load conditions. The experiment was performed using water cooled common rail direct injection (CRDI) diesel engine with prepared D-WPO blend. Different characteristics such as In-cylinder pressure (CP), heat release rate (HRR), ignition delay time (IDT), brake thermal efficiency (BTE), brake specific fuel consumption (BSFC) and exhaust gas temperature (EGT), carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide (NOx) and smoke opacity emission are studied with respect to the effect of different blends and applied load used. It was observed that increasing of CeO2 nanoparticles in blend improved the overall performance and emission of the engine. Form the results, D-WPO30+Ce100 blend showed enhanced brake thermal efficiency (BTE), brake specific fuel consumption (BSFC) and exhaust has temperature (EGT) are 28.2%, 3% and 465oC respectively. Similarly, reduced emission of CO, NOx, HC and smoke opacity was observed in the CeO2 added blends particularly at 100 mg/L. It was concluded that among all blends prepared, the D70:WPO30 with 100 mg/L of CeO2 showed improved combustion, performance and emission characteristics in proposed diesel engine.

Model-Based Two-Stage SCR Urea Injection Strategy for Diesel Engine to Meet Low NOX Emission Regulation

Model-Based Two-Stage SCR Urea Injection Strategy for Diesel Engine to Meet Low NOX Emission Regulation

Alternative Analyzers for the Measurement of Gaseous Compounds During Type-Approval of Heavy-Duty Vehicles

Emissions standards describe the fuels, the procedures, and, among others, the analyzers to be used for the measurement of the different compounds during the type-approval of heavy-duty engines and vehicles. Traditionally, NOx, CO, hydrocarbons, and CO2 were the gaseous compounds measured within the Euro standard, with the later addition of CH4 and NH3. Euro 7, introduced in early 2024, expanded those compounds, requiring the measurement of N2O and HCHO. With an increasing number of molecules that need to be measured and introducing carbonless fuels, such as hydrogen, that present different requirements compared to carbon-based fuels, the test procedure needs to be updated. The performances of three laboratory-grade instruments and three portable emissions measurement systems based on Fourier-transformed infrared (FTIR) or quantum cascade laser infrared (QCL-IR) technologies were investigated while measuring from the tailpipe of a Diesel engine and a compressed natural gas (CNG) vehicle. All instruments presented good agreement when emissions of NOx, CO, CH4, NH3, N2O, HCHO, and CO2 were compared using: Z-score, F-test and two tail t-test of student. Water concentration measured by the four FTIRs was also in good agreement. Moreover, the dry emissions of CO2 and CO measured by the laboratory non-dispersive infrared (NDIR) and corrected using water were a few percentages different from those obtained using the regulated carbon-based approach. The results indicate that all the investigated systems are suitable for the measurement of the investigated gaseous compounds, including CO2 and H2O.

Experimental Study of Hydrogen Use in a Diesel Engine in Automotive

<p style="text-align:justify;text-indent:36.0pt;"><span style="font-family:"Times New Roman","serif";font-size:12pt;line-height:200%;">The main objective of this experiment is to reduce the major pollutants NO and particulate matter that is emitted by diesel engines to avoid green house gases. The critical part is that   reducing both the NO and particulate matter simultaneously is not possible. If we try to reduce PM, NO increases     and vice versa. Based on this concept in this research, hydrogen is used in addition to diesel, as hydrogen represents a good alternative fuel to reduce emissions. Some experimental aspects with respect to hydrogen flow 0.024, 0.041, 0.08 and 0.09 kg per hour along with diesel fuel. The amount of    hydrogen injected into the chamber will be compensated by reducing the diesel quantity 1.081, 1.030, 0.94 and 0.866 kg per hour at one fourth, half , three fourth and full load respectively, at a speed of 1500 rpm water cooling. The engine is equipped with  Engine Soft software that captures  and stores the data. In the first phase, the experiment was conducted using diesel fuel and in the second phase the diesel fuel and hydrogen at different flow rates were used to enhance the combustion. At full load for 0.041 kg per hour, the gas of hydrogen CO was reduced by 37.5%, HC by 60%,NO by 22.45%. CO<sub>2   </sub>was reduced by 45.8% at 0.08 kg per hour of hydrogen. At 0.09 kg per hour of hydrogen injection, the particulate matter was decreased by 79.6%. At full load and for 0.09 kg per hour flow rate, the brake and indicated thermal efficiency was increased by 33.4% and 32.4%, respectively.The main objective of this experiment is to reduce the major pollutants NO and particulate matter that is emitted by diesel engines to avoid green house gases. The critical part is that   reducing both the NO and particulate matter simultaneously is not possible. If we try to reduce PM, NO increases     and vice versa. Based on this concept in this research, hydrogen is used in addition to diesel, as hydrogen represents a good alternative fuel to reduce emissions. Some experimental aspects with respect to hydrogen flow 0.024, 0.041, 0.08 and 0.09 kg per hour along with diesel fuel. The amount of    hydrogen injected into the chamber will be compensated by reducing the diesel quantity 1.081, 1.030, 0.94 and 0.866 kg per hour at one fourth, half , three fourth and full load respectively, at a speed of 1500 rpm water cooling. The engine is equipped with  Engine Soft software that captures  and stores the data. In the first phase, the experiment was conducted using diesel fuel and in the second phase the diesel fuel and hydrogen at different flow rates were used to enhance the combustion. At full load for 0.041 kg per hour, the gas of hydrogen CO was reduced by 37.5%, HC by 60%,NO by 22.45%. CO<sub>2   </sub>was reduced by 45.8% at 0.08 kg per hour of hydrogen. At 0.09 kg per hour of hydrogen injection, the particulate matter was decreased by 79.6%. At full load and for 0.09 kg per hour flow rate, the brake and indicated thermal efficiency was increased by 33.4% and 32.4%, respectively.</span></p>

Energy-exergy analyses of hydrogen enriched⸺ diesel and blended biofuel (Azolla pinnata macroalgae) on the dual fuel diesel engine

Hydrogen fuel has gained global attention as a potential alternative to conventional fuels as it reduces greenhouse gas emissions and addresses energy sustainability challenges. In addition, biofuel (Azolla pinnata) is highly productive having limited negative impacts with an exemplary productivity rate. The energy-exergy analysis in CI engine's is an effective method for determining its efficiency and effectiveness. This paper highlights the effects of diesel, H2 enriched diesel, and H2 enriched B40 (60% diesel + 40% Algal Biodiesel) on the energetic and exergetic efficiency of a dual-fuel diesel engine with a rated speed and power of 1500 rpm and 3.5 kW respectively. The analysis was done at varying engine loads: low loads (25%), medium loads (50%), and high loads (75%), respectively. The energy and exergy for 40% hydrogen-enriched B40 increased by 8.77% and 23.85%, respectively, compared to neat diesel operation at higher loads. In addition, the irreversibility of 40% hydrogen-enriched B40 decreased by 13.82% at higher load conditions as compared to base diesel operation. The sustainability index of 40% hydrogen-enriched B40 was 1.38 compared to 1.28 of diesel, showing an improvement of 7.82%. The theoretical energy-exergy analyses showed an error less than 5% compared to BTE validating the results of the energy-exergy analyses performed theoretically.

Cascaded Integral Minus Tilt Integral Derivative With Filter for Frequency Stabilization of V2G/G2V Enabled Hybrid Microgrid

ABSTRACTRenewable generation plays an important part in today's power system. With the inclusion of the inverter interfaced renewable energy sources (RESs) into a microgrid, the total system inertia decreases and it leads to increased frequency deviation in presence of a disturbance. This paper proposes a cascaded Integral Minus Tilt Integral Derivative with Filter (I–TDN)‐Proportional‐Integral (PI), [(I‐TDN)‐PI] controller for frequency stabilization of a hybrid microgrid in presence of electric vehicles (EV). The microgrid model includes reheated thermal power plant with high degree of non‐linear system such as inverter based RESs like photovoltaic and wind generation systems. A diesel engine generator is incorporated for load frequency control during perturbation in the system frequency. Virtual inertia controller (VIC) with inverter based energy storage system (ESS) is commonly used to improve system inertia and frequency stability of the microgrid. In addition to the ESS, this paper proposes inclusion of the EVs in this VIC. The optimal gains of the proposed cascaded I‐TDN‐PI controller are determined using Mountain Gazelle Optimizer (MGO), a modern metaheuristic optimization algorithm. Sensitivity of the proposed controller is investigated in presence of system nonlinearities, load perturbations, time delay, system parameter variation and RES power fluctuations. The simulation results justify the robustness of the proposed control structure for frequency stabilization of the microgrid.

Evaluating Biodiesel Properties from Waste Cooking Oil for Sustainable Energy Applications

Biodiesel was synthesized from used vegetable oils collected from local restaurants in Minna, Niger State, Nigeria, using a base-catalyzed transesterification process with methanol and potassium methoxide as the catalyst. The physicochemical properties of the produced biodiesel, such as density, kinematic viscosity, flash point, pour point, cetane number, and calorific value, were evaluated and compared against conventional diesel fuels and biodiesel from other sources like Jatropha, Neem, and Castor oils. Gas chromatography (GC) was used to analyze the fatty acid methyl esters (FAMEs) composition, identifying methyl oleate, methyl linoleate, methyl palmitate, and methyl stearate as the primary components. The produced biodiesel exhibited favourable properties, including a cetane number and flash point within recommended ASTM standards, indicating efficient ignition and safe storage characteristics. Additionally, the calorific value and kinematic viscosity of the biodiesel were found to be comparable to conventional diesel, making it a viable blend for diesel engine applications.

TDOF PID Controller for Enhanced Disturbance Rejection with MS-Constraints for Speed Control of Marine Diesel Engine

This study proposes a two-degree-of-freedom PID controller design and tuning method based on a simple pole placement approach to enhance servo and regulatory performance while ensuring the stability of diesel engines. In the modeling of the control target, the actuator is analytically modeled. In contrast, the type of model for the diesel engine is derived analytically, and its parameter estimation uses operational data from naval ships. The proposed controller consists of a PID controller to improve regulatory performance and a set-point filter to enhance servo response. PID controller parameters consist of the parameters of the controlled plant model and a single tuning variable. At the same time, the set-point filter comprises the controller parameters and a single weighting factor. To ensure the robust stability of the controller, the controller parameters are tuned based on the maximum sensitivity. To verify the effectiveness of this study, simulations for the speed control of a diesel engine with inherent nonlinearity were conducted under three scenarios. Performance was quantitatively analyzed using the integral of time-weighted absolute error, 2% settling time, 2% recovery time, specified maximum sensitivity, and maximum peak response value, and was compared with Skogestad’s IMC and Lee’s IMC. Based on evaluation indices, the proposed controller demonstrated superior performance in both servo and regulatory responses compared to the two existing control techniques while ensuring stability.

Analysis the Principle and Applications for Locomotive Engine

Abstract. The evolution of locomotives is the cornerstone of modern transport and has had a profound impact on economic growth and social mobility. From the pioneering steam locomotives of the 19th century, which marked the beginning of a transformative journey for rail transport, to today's complex diesel and electric locomotives, each technological advance has shaped the efficiency, speed and environmental impact of rail systems. With this in mind, this study will offer a systematically analysis for the principle as well as applications for such engine. Steam locomotives revolutionized the transportation of goods and passengers, laying the foundation for the future of rail travel. Diesel locomotives further enhance operational flexibility and reliability, while electric locomotives are becoming mainstream due to their energy efficiency and low emissions. This study explores the historical development of locomotives, highlighting key technological milestones and their impact on rail transport. Meanwhile, the current advances in locomotive technology, including the integration of hybrid power systems and alternative energy sources, are studied. As the rail industry faces increasing pressure for sustainability, it is important to understand the evolution and future prospects of locomotives. By analyzing these developments, this paper aims to provide insights into different locomotive principles and how locomotive technology is evolving in an era of increased environmental awareness and technological innovation, shaping the future of rail transportation.

Analysis of the Principle and Applications of Four-stroke Engines in Transportation

Abstract. Four-stroke engines a type of internal combustion engine (IC engine) that can turn the heat provided from the fuel to work, and they are mainly classified as two groups, which are gasoline engines and diesel engines. Four-stroke engines can be applied to high power machines because of its high thermal efficiency. In four-stroke engines, the piston reaches the dead center four times in the cylinder to complete a cycle. This cycle includes the taking in of gas, the compression, the ignition, the expansion and the exhaustion of gas. In gasoline engine, this cycle is called the Otto cycle, and in diesel engine, this cycle is called the Diesel cycle. The greatest difference between these two engines is that they burn different types of fuel. In that way, the procedure of converting the heat to work is different. To help this cycle performs better economically and more efficiently, additional attachments such as hybrid engine and computer assistance are used. This research summarizes and analyses the application of four-stroke engines in land transportation, in aviation and in marine transportation, and this article gives a possible prediction to the future trend of the technology advancements of engines in transportation based on the analyses.

Multi‐aspect assessment and multi‐objective optimization of preheated tallow biodiesel‐diesel blend as alternate fuel in CI engine

AbstractThis study meticulously examined the impact of preheated tallow biodiesel on the performance and emission characteristics of a diesel engine. Employing a single‐cylinder, water‐cooled diesel engine configured with exhaust gas recirculation in this investigation, exhaust gas temperature (EGT) could be used to preheat the biodiesel, reducing its viscosity and density. This improvement in viscosity and density could enhance the injection process, which is often hindered by the higher density and viscosity of biodiesel compared with diesel fuel. The investigation achieved a peak preheat temperature of 70°C for the biodiesel, leading to notable improvements in brake thermal efficiency and brake power, particularly under high‐load conditions. A significant reduction in emissions was observed, with hydrocarbon and carbon monoxide levels decreasing by 46.87% and 50%, respectively, when using preheated biodiesel. To refine the engine's performance further, this study utilized response surface methodology (RSM) for the optimization of operational parameters, including injection timing, engine load, and biodiesel preheat temperatures. Optimal conditions were identified at an injection timing of 21° before top dead centre, a preheat temperature of 64°C, and an engine load of 45.45% for which output response was 18.68% brake thermal efficiency, 307°C EGT, 0.0247% vol. CO, 15.32 ppm hydrocarbons, and 131.37 ppm nitrogen oxides (NOx). The successful implementation of preheated tallow biodiesel signifies a crucial step forward in the pursuit of a more sustainable and efficient transportation industry. This advancement holds the promise of reducing reliance on traditional fossil fuels, thereby contributing to the global efforts towards achieving a more environmentally friendly energy landscape.

Optimization of Biodiesel–Nanoparticle Blends for Enhanced Diesel Engine Performance and Emission Reduction

Optimization of Biodiesel–Nanoparticle Blends for Enhanced Diesel Engine Performance and Emission Reduction

Cycle analysis and environmental assessments of cascade organic rankine cycle on diesel engine ships

This study investigates the application of organic Rankine cycle (ORC) on ships to reduce fuel oil consumption and assess improvements in the Energy Efficiency Existing Ship Index (EEXI), and carbon intensity indicator (CII). A cascade ORC(C-ORC) configuration is designed to utilize the exhaust gas from a diesel engine.Thermodynamic simulation identified a combination of toluene and R1233zd as the optimal working fluids for the C-ORC. Exergy analysis was conducted to evaluate the performance difference between the C-ORC system and a version with an internal heat exchanger (C-IHX ORC). The results showed a maximum exergy efficiency of 56.78 % for the C-IHX ORC, compared to 49.33 % for the C-ORC. Further evaluations of the C-IHX ORC, including fuel savings, energy generation, EEXI, and CII, demonstrated that average vessel fuel consumption decreased by 1.02 %, and average attained EEXI improved by 0.93 %. Additionally, the attained CII value was enhanced by 0.98 % on average, depending on operating loads and traveled distances. Although the improvements of EEXI, and CII offered were modest, they present the potential for further enhancement through the utilization of additional waste heat sources, such as economizer steam, and jacket cooling water.

Experimental verification of changes in the control map of a diesel engine operation due to fuel consumption

The paper describes an experiment related to the introduction of changes in the control software of a supercharged diesel engine in order to reduce fuel consumption, as a measure of useful efficiency. The map shaping the torque in the range of low and medium engine speeds was modified. The fuel dose for a specific engine speed at maximum engine load was changed and the boost pressure was increased, without exceeding the permissible values. A vehicle from the age group of 16 years - typical for the automotive market in Poland, was selected for the tests. It meets the EURO 5 standard. The experiment was carried out on a chassis dynamometer and in road traffic conditions. The average fuel consumption was obtained lower by 0.4 dm3 per 100 km than the factory assumed.

Investigation on CuO nanoparticle enhanced mahua biodiesel/diesel fuelled CI engine combustion for improved performance and emission abetted by response surface methodology

In this study, the characteristics of diesel engines were tested with in-house produced mahua biodiesel blended with diesel and copper oxide nanoparticles (CuO NP) catalyst. The preliminary investigation used mahua biodiesel-diesel blends (M10, M20, and M30) among them M20 outperformed. Further M20 and CuO NP with concentrations of 25, 50, and 75 ppm are studied. Finally, the response surface methodology (RSM) was used to determine the appropriate NP concentration for M20. The findings showed that the blend of M20 with 60 ppm NP at 80% load had the highest desirability (0.9740), and the developed RSM model predicted engine responses with a mean absolute percentage error (MAPE) of 3.0962% to the confirmation test confirming the model’s accuracy. The optimized M20NP60 blend demonstrated superior combustion, performance and emission characteristics.

Coal Mine Dust Size Distributions, Chemical Compositions, and Source Apportionment

Current regulations mandate the monitoring of respirable coal mine dust (RCMD) mass and crystalline silica in underground coal mines to safeguard miner health. However, other RCMD characteristics, such as particle size and chemical composition, may also influence health outcomes. This study collected RCMD samples from two underground coal mines and performed detailed chemical speciation. Source apportionment was used to estimate RCMD and silica contributions from various sources, including intake air, fire suppression limestone dust, coal dust, diesel engine exhaust, and rock strata. The mine dust mass-based size distributions were comparable to those recorded over a decade ago, with a peak around 10 μm and the majority of the mass in the supermicron size range. The current mine conditions and mining practices do not appear to have significantly increased the generation of smaller particles. Limestone rock dust was prevalent in many locations and, along with coal dust, was the main contributor to RCMD at high-concentration locations. Silica accounted for over 10% of RCMD mass at several active mining locations, primarily from limestone and rock strata dust. Reducing the concentration of limestone dust and its silica content could reduce RCMD and silica levels. Further cleaning of the intake air could also improve the overall mine air quality.