Constant Rpm Research Articles

Assessment of Synchrophasing for a Pair of Rotors in Close Proximity

This paper investigates the aerodynamics and aeroacoustics of a pair of rotors within the “Radiation and Propagation for Multirotor Systems” project from the Group for Aeronautical Research and Technology in Europe (GARTEUR) Action Group 26. The study employs validated high-fidelity computational fluid dynamics (CFD), the in-house Helicopter Multi-Block Solver 3 (HMB3), to investigate a pair of dual-bladed 13x7 rotors in hover and edgewise flights. The study aims to reduce rotor noise by introducing a phase offset between the starting positions of the rotors in tandem configurations. The rotors maintained a constant RPM, and a tip Mach number of 0.4, close to typical values for full-scale urban air mobility (UAM) rotorcraft. Results indicated a performance loss from tandem rotors compared to isolated configurations, especially for the downstream rotor. However, the performance of the downstream rotor is slightly recovered in the tandem offset configuration. A comprehensive synchrophasing study based on cumulative effect of the rarefaction and compression in the acoustic wave is also presented, showing different levels of noise reduction without compromising performance. More than 20 dBA of noise reduction was observed in several one-third octaves bands, and up to 7 dBA of overall noise reduction was achieved at optimal de-phased cases for the region between the two rotors. In the meantime, the most beneficial phases can be adjusted to achieve maximum noise reduction at different locations, including upstream, inter-rotor, and downstream regions. Furthermore, transforming from a single isolated rotor to the optimal de-phased tandem offset configuration while producing the same amount of lift achieved almost 10 dBA noise reduction, suggesting a perceived noise that is 50% lower in reality.

Same-spot micro-ECM based on constant-accelerated movement of the electrode

ABSTRACT An injector nozzle needs a precision upside-down tapered-microhole, and the nozzle material is often a high temperature corrosion resistant alloy that is very difficult to machine. In this study, a same-spot micro-ECM technique with the electrode in “constant-accelerated movement” was proposed. Insulated by electrophoretic deposition, an ultra-fine electrode was inserted deep into the hole and subject gradually to withdrawal from the hole at constant rpm and acceleration. The electric flux intensity acting on the hole-wall gradually decreased and so did the material dissolution rate on the hole-wall, thus creating an upside-down tapered hole with the desired taper-rate. The experiments’ results showed that upside-down tapered holes with taper-rates of T(a=1) = 0.094 (Ra 0.593 μm) and T(a = 2) = 0.02 (Ra 0.435 μm) were produced when the electrode was subject to constant-acceleration withdrawal at 1.0 and 2.0 μm/s2, respectively, and respective spray angles of 31° and 23° were created. The proposed technique is commercially promising in industry.

An experimental study of the performance of a CI engine using ethanol as a fuel stabilizer

Ethanol is a promising alternative fuel owing to its renewable bio-based origin and lower carbon content, as well as its ability to significantly reduce particle emissions in diesel engines. To evaluate the particulate matter emissions and performance of ethanol-diesel blends, researchers conducted experiments using mineral blends of 5% and 10% ethanol with 95% and 90% diesel fuel, respectively, as well as biodiesel blends with 25% biodiesel and 75% diesel fuel, and 100% diesel as a baseline. These blends were tested in a CI engine with a constant RPM of 1350 and variable loads from 0.0 to 1.6 at intervals of 0.2 kg-m. The study found that biodiesel blends reduced exhaust particulate emissions compared to diesel fuel, while the brake specific fuel consumption decreased with increasing brake power, and the brake thermal efficiency increased as brake power increased. The sound pressure level was measured from different locations of the engine, and the results indicated that increasing the percentage of biodiesel led to a decrease in the sound pressure level. Overall, the study concluded that ethanol-blend fuel improved both brake and engine thermal efficiency while reducing particulate matter emissions. The engine experiments evaluated engine brake torque, braking power, brake specific fuel consumption, brake thermal efficiency, and particulate matter emissions under a variable load and a constant engine speed.

Wear factors and mechanisms of L-80 steel casings

Casing wear in directional drilling is inevitable and may result in catastrophic failure of the casing column. It is thus essential to understand its mechanisms and quantify its extent by estimating the casing wear factor. In this research, actual field casing samples, drilling pipe joints and muds were considered. An in-house built testing facility was used to test several L-80 casing samples by considering three rotational speeds of the drill pipe tool joint (DP-TJ) (115, 154, and 207 rpm) and three side loads (1000 N, 1200 N and 1400 N). The influence of the water- and oil-based muds on the coefficient of friction, wear volume, wear factor and wear mechanisms were investigated. The results revealed that under water-based mud (WBM) lubrication casing wear volume and wear factors were more than twice that of oil-based mud (OBM) lubrication. Moreover, it was observed that as the side load increased under both OBM and WBM lubrication at a constant rpm, both wear volume and wear factor increased. However, increasing the rotational speed while maintaining the side load constant decreased the wear factor, owing to the localized softening effect caused by the high heat generation at the contact area and the possible hydrodynamic lubrication regime change at higher speeds. The analysis of the digital microscopic images taken at the wear region shows that abrasive mechanism was dominant in the case of OBM lubrication. On the other hand, both abrasive and adhesive wear mechanisms were present under WBM lubrication.

Experimental Study on Combustion Characteristics and Regulated and Unregulated Emissions of a Common-Rail Diesel Engine Fueled with Waste Cooking Oil Biodiesel

<div>The demand for fossil fuels can be reduced and environmental harm can be minimized by producing biodiesel from used cooking oil. This article was focused on investigating the combustion characteristics and regulated and unregulated emissions of a common-rail diesel engine fueled with different mixed concentrations of biodiesel and diesel fuel, including pure diesel fuel (B0), B10 (diesel containing 10%vol of biodiesel), B20, and B30. Experiments were conducted with three engine loads, corresponding to brake mean effective pressures (BMEP) of 0.289 MPa, 0.578 MPa, and 0.867 MPa at a constant speed of 1540 rpm. At medium and high loads, the waste cooking oil biodiesel (WCOB) increased in-cylinder pressure, advanced both the peak heat release rate and heat release center (CA50), shrunk the ignition delay (ID), and extended combustion duration (CD). The high viscosity of B30 blends under low load worsened the spray and led to poor combustion. Under high-load conditions, carbon dioxide (CO<sub>2</sub>) and nitrogen oxides (NO<sub>x</sub>) emissions increased by 14.3% and 3.1%, while carbon monoxide (CO), soot, and total hydrocarbon (THC) emissions decreased by 13.3%, 31.4%, and 30.37%, respectively, for the B30 blend compared to diesel. The emission trends for nitrogen dioxide (NO<sub>2</sub>), formaldehyde (HCHO), methane (CH<sub>4</sub>), ammonia (NH<sub>3</sub>), ethylene (C<sub>2</sub>H<sub>4</sub>)<sub>,</sub> and formic acid (HCOOH) were consistent with increasing volume ratios of WCOB under the three loads. And they had the lowest emissions at 75% load for B30, with reductions of 70.5%, 66.7%, 18.4%, 78.8%, 13.2%, and 84.6%, respectively, compared to diesel. Acetaldehyde (MECHO) emissions increased with increasing WCOB blending volume ratio at 25% load condition and were highest at the B30 blend. The above results show that the B30 blend is the most effective in reducing unregulated emissions under all three load conditions, especially at medium and high loads.</div>

Particulate emissions and soot characterisation of diesel engine exhaust for steady-state operating condition using dioctyl phthalate blends with diesel

The study investigates the particulate emission and soot characterisation of particles originating from a six-cylinder common-rail direct injection (CRDI), turbocharged diesel engine. The experiments were conducted using steady-state operating conditions, a constant rpm of 1500 and four different engine loads (25, 50, 75, and 100%). Three different fuels were tested: neat diesel and two dioctyl phthalate (DOP) blends with diesel (DOP10 and DOP20). Particulate emissions were measured using DMS500 and collected on transmission electron microscope (TEM) grids for further analysis of the morphology and nanostructure of the soot structure. The particle number and mass concentrations for neat diesel were found to be lower than DOP fuel blends for all four loads. The primary particle diameter increases with increase in the engine load and decreases with an increase in DOP fuel content in the blend. A compact structure of soot aggregate was observed for DOP fuel blends compared to that of diesel and it increased with an increase in the engine load. Short and curved fringes were observed for DOP fuel blends. Also, an increase in fringe length and a reduction in fringe tortuosity was observed with an increase in engine load. The fringe separation distance results show an opposite trend with respect to fringe length and fringe tortuosity for DOP fuel blends i.e. less inter-planar spacing was observed for DOP fuel blends compared to that of diesel. This would result in an overall decrease in the oxidation reactivity of soot particles.

Negative impact of constant RPM control strategy on ship NOx emission in waves

In severe wave conditions, the ship propulsion system is loaded with high fluctuations due to external disturbances. The highly fluctuating loads enforce radical changes in the main engine torque, which in turn demands variation of the fuel rate injected into the cylinders if a constant rotational speed strategy is applied. Therefore, the temperature of gases varies to a large extent during the combustion process in the cylinders. The emitted NOx is a function of this highly fluctuating temperature. The main goal of this study is to investigate NOx emission under the aforementioned conditions when a usual constant RPM control strategy is applied in waves similar to the calm water condition. The paper presents a mathematical model of the whole system, which is applied to a selected ship both in regular waves and in calm water conditions. The results show that the sea waves, in comparison with the calm water condition, can radically increase the emitted NOx under the constant rotational speed strategy. This change can reach even 1014 times more, averagely. The results also show that the higher the wave height the higher the emitted NOx. It is concluded that the control strategy of keeping the engine rotational speed in waves at a constant level is the most important reason for the significantly increased NOx emission in waves in comparison with the calm water condition.

Analysis of Particulate Matter Emissions and Performance of the Compression Ignition Engine Using Biodiesel Blended Fuel

As the world becomes more urbanized, the market for petroleum products increases. The supply of crude oil-based products such as diesel, gasoline, and natural gas is limited. Furthermore, natural resources are finite and their reservoirs are located in certain parts of the globe. Countries with low to no fossil fuel resources are experiencing a scarcity of petroleum products, necessitating the exploration of alternative energy resources. In this research, tests regarding the exhaust particulate emission, sound pressure level, and performance have been carried out using samples from diesel and biodiesel (waste cooking oil) blended fuel. Two fuel samples have been used, B25 (biodiesel 25% and 75% diesel) and 100% diesel as a baseline in a CI engine at constant RPM of 1350 and variable loads of 0.0 to 1.6 at an interval of 0.2Kg-m. The results show that particulate emissions are reduced by about 7.29% when using biodiesel blended fuel, whereas brake-specific fuel consumption of biodiesel blended fuel has decreased as brake power increased, and brake thermal efficiency increased as brake power increased. The sound pressure level was measured from different locations of the engine (back, front, left) and for varying load. The results show that B25 produces less noise than D100 in each case.

Modification of Cold-Sprayed Cu-Al-Ni-Al2O3 Composite Coatings by Friction Stir Technique to Enhance Wear Resistance Performance

An innovative hybrid process combining two effective surface modification techniques, cold spray (CS) and friction stir processing (FSP), was proposed to refine the microstructure of Cu-Al-Ni-Al2O3 composite coating material. FSP was performed under constant rpm using extensive cooling conditions to remove heat generated during the operation. Microstructural characterizations such as optical micrography (OM), scanning electron microscopy (SEM), Electron Backscatter Diffraction (EBSD), Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were performed to evaluate the microstructural evolution of the coatings before and after FSP treatment. Mechanical characterizations such as microhardness and elastic modulus were measured using micro-depth sensing techniques. Furthermore, sliding wear tests were performed to study the wear resistance of the as-sprayed and processed coatings. The findings suggest that after FSP, there is an improvement in microstructure of the coating layers with the elimination of particle boundaries, micro-pores and micro-cracks, and processed coatings showed an improvement in mechanical properties. Furthermore, there was a slight reduction in the wear rate of the deposited CuAlNi-Al2O3 composite coatings. Among all the test coatings, friction stir processed S1 coating showed the lowest wear rate, which was an almost two times lower wear rate than its unprocessed counterparts.

CFD Validation and Aerodynamic Behaviour of NREL Phase VI Wind Turbine

In the present study, the 3D flow around the rotating wind turbine whose blade’s geometry is tapered and twisted is observed by using Computational Fluid Dynamics (CFD) as a numerical simulation tool. The CFD simulation of the wind turbines is essential for their efficient use and optimization of the solutions. This paper shows the accuracy of numerical simulation of Reynolds Averaged Navier Stokes equations (RANS equations) along with the Shear Stress transport k-ω turbulence model and validation with the experimental data by the National Renewable Energy Laboratory. All the simulations in this paper are performed on the sequence S of the test configuration of the experiment conducted at the NASA Ames Wind tunnel facility with the blades rotating at constant RPM and varying inlet wind speeds. The results of this study depict a close agreement with the experimental data. The torque predicted by this method is well in line with the experimental values, and it is also able to predict the stalling regions of the wind turbine. This study captures the pre-stall, stall & deep-stall regions and also the 3-dimensional flow around the wind turbine. The flow separation starts occurring on the wind turbine when the inlet speed is greater than 10 m/s, and it is observed that the turbine goes into the deeps stall region when the wind speed is 18m/s.

Estimation of Elbow Wall Thinning Using Ensemble-Averaged Mel-Spectrogram with ResNet-like Architecture.

An elbow wall thinning diagnosis method by highlighting the stationary characteristics of the operating loop is proposed. The accelerations of curved pipe surfaces were measured in a closed test loop operating at a constant pump rpm, combined with curved pipe specimens with artificial wall thinning. The vibration characteristics of wall-thinned elbows were extracted by using a mel-spectrogram in which modal characteristic variation shifting can be expressed. To reduce the deviation of the model’s prediction values, the ensemble mean value of the mel-spectrogram was used to emphasize stationary signals and reduce noise signals. A convolutional neural network (CNN) regression model with residual blocks was proposed and showed improved performance compared to the models without the residual block. The proposed regression model predicted the thinning thickness of the elbow excluded in training dataset.

CFD and system-based investigation on the turning maneuver of a twin-screw ship considering hull-engine-propeller interaction

Ship maneuver is a dynamic process accompanied by strong interaction among hull, engine, and propeller, and the interaction phenomenon is more complicated for twin-screw ships. In this paper, numerical investigation on the turning maneuver of a twin-screw ship considering hull-engine-propeller interaction is carried out by using CFD and system-based methods. Taking the twin-screw ship ONRT model as the study object, a series of captive model tests are simulated by using RANS method. Based on the computed global loads on the propellers and the corresponding flow field details, the hydrodynamic characteristics of the propellers operating under the maneuvering conditions are analyzed. The effective wake fraction is computed and the mathematical model of propeller performance under the maneuvering conditions is obtained through data fitting. Based on the established mathematical model, the turning circle maneuver considering hull-engine-propeller interaction is simulated. Three control strategies of main engine, i.e., constant RPM, constant torque, and constant power, are considered. The effects of the control strategies on the turning motion and the propulsive loads during turning motion are explored. This study is useful to provide a deeper insight into the ship maneuvering behaviors and the propeller characteristics during maneuvering motion under the influence of hull-engine-propeller interaction.

Designing Low-Cost Arduino Powered Spin Coater for Thin Film Deposition

In the present work, we have designed a low-cost spin coater using the Arduino Uno board. The advantage of selecting Ardunio is, it has pulse width modulation (PWM) based pins. Depending on the width of the pulse, the output voltage changes which will intern changes the speed of the DC motor connected to the PWM pin. The thickness of deposited film using spin coater depends on RPM and duration of rotation. The rotation of the substrate during deposition has three stages a gradual increase in RPM, maintaining constant RPM over a while, and a gradual decrease in RPM. All these parameters can be controlled by an Arduino board. An Aluminum doped Zinc Oxide film was deposited on glass substrate using Arduino based spin coater. X-ray diffraction, UV – VIS spectroscopy, and FTIR methods were used as characterization techniques. Hexagonal crystal structure of deposited AZO layer was confirmed by XRD and optical band gap, transparency were calculated by UV-VIS spectroscopy.

A Validation Study of the Aerodynamic Behaviour of a Wind Turbine: Three-Dimensional Rotational Case

Numerical modelling and simulation of a rotating, tapered, and twisted three-dimensional blade with turbulent inflow conditions and separating flows is a challenging case in Computational Fluid Dynamics (CFD). The numerical simulation of the fluid flow behaviour over a wind turbine blade is important for the design of efficient machines. This paper presents a numerical validation study using the experimental data collected by the National Renewable Energy Laboratory (NREL). All the simulations are performed on the sequence S of the extensive experimental sequences conducted at the NASA/Ames wind tunnel with constant RPM and variable wind speeds. The results show close agreement with the NREL UAE experimental data. The CFD model captures closely the totality of the defining quantities. The shaft torque is well-predicted pre-stall but under-predicted in the stall region. The three-dimensional flow and stall are well captured and demonstrated in this paper. Results show attached flow in the pre-stall region. The separation appears at a wind speed of 10 m/s near the blade root. For V>10m/s, the blade appears to experience a deep stall from root to tip.

Experimental evaluation of diesel engine operating with A TERNARY BLEND (BIODIESEL-DIESEL-ETHANOL)

The present investigation aims to study the future potential fuel of a non-edible tamanu oil (calophyllum inophyllum). The raw oil of tamanu oil was converted into biodiesel in two-step esterification process and different test fuel blends with biodiesel were prepared with conventional diesel and ethanol as an additive to evaluate its effect on engine characteristics such as BP, BTE, and BSFC, EGT and smoke density on a 4.4 kW rated power, single-cylinder four-stroke of constant rpm C.I. engineat different loads (25%, 50%, 75%, and 100% of rated power). The fuel blends were prepared with biodiesel in the ratio of 40%,100% coded as B40 and B100 respectively along with diesel fuel and ethanol as an additive in the fixed ratio of 10%, 15%, and 20%. It was found that B40E20D40 showed a reduction in smoke density and BSFC of 14.28% and 5.9% respectively, 18.3% increase in BTE and 3.73% reduction in exhaust gas temperature at full load whereas B100 showed a maximum reduction in smoke density of 15.97% with 4.53% increase in BSFC and a marginal increase in EGT of 0.53%. B40E20D40 gave a better performance in a diesel engine from the perspective of minimum BSFC, lower exhaust gas temperature and higher BTE among all other blends.

Experimental investigation of various ethanol blends impact on combustion and emissions characteristics of diesel ignited dual fuel HCCI engine

Purpose Homogeneous charge compression ignition (HCCI) engine is an advanced combustion method to use alternate fuel with higher fuel economy and, reduce NOX and soot emissions. This paper aims to investigate the influence of ethanol fraction (ethanol plus gasoline) on dual fuel HCCI engine performance. Design/methodology/approach In this study, the existing CI engine is modified into dual fuel HCCI engine by attaching the carburetor to the inlet manifold for the supply of ethanol blend (E40/E60/E80/E100). The mixture of ethanol blend and the air is ignited by diesel through a fuel injector into the combustion chamber at the end of the compression stroke. The experiments are conducted for high load conditions on the engine i.e. 2.8 kW and 3.5 kW maximum output power for 1,500 constant rpm. Findings It is noticed from the experimental results that, with an increase of ethanol in the blends, ignition delay (ID) increases and the start of combustion is retarded. It is noticed that E100 shows the highest ID and low in-cylinder pressure; however, E40 shows the lowest ID compared to higher fractions of ethanol blends. An increase in ethanol proportion reduces NOX and smoke opacity but, HC and CO emissions increase compared to pure diesel mode engine. E100 plus diesel dual-fuel HCCI engine shows the highest brake thermal efficiency compared to remaining ethanol blends and baseline diesel engine. Originality/value This experimental study concluded that E100 plus diesel and E80 plus diesel gave optimum dual fuel HCCI engine performance for 2.8 kW and 3.5 kW rated power, respectively.

Effect of Pilot and Post Injection Timing on Combustion, Emission and Performance of a Diesel Engine

The emissions and combustion properties of a diesel engine is studied in this article for the effect of pilot and post injection. An Automotive CRDI single-cylinder Diesel Engine of 625 cc capacity was used to perform tests at 50 percent loading condition with main fuel injection timing fixed at 15° BTDC and engine running at a constant rpm of 1400. The pilot injection timing and quantity is varied as 5°, 10°, 15° and 20° BTDC and 5 to 20% respectively. The mass of fuel injected in post injection is varied from 2 to 5 mg/cycle. There is a decrease in NOx and increase in Brake Thermal Efficiency with the advancement in quantity & timing of pilot injection. The variation in NOx emission has been seen almost same when fuel is injected with variation in mass quantity (mg/cycle) and timing of post injection.

Surveillance FPV Drone with Obstacle Avoidance System

The unmanned air vehicle (UAV) is mostly used in inspection and surveillance operations recent. The UAV is also termed as vertical take-off landing (VTOL), since it is capable of vertical take-off and landing without need of a runway. The big tunnels, infrastructure and large bridges are inserted using UAV by photographic inspection. UAVs are also used for surveillance purposes by the military and by the security guards. Since this is a new technology of the last decade, deep research has to be done. UAVS have the cross structure arrangement to which the rotor blades are attached at the end points of cross beams. These rotors are driven by the DC brush motors and motors are powered by the lithium ion rechargeable battery. The working principle of quad- rotors is the same as the chopper by controlling the rpm of each rotor blade, due to which the gyroscopic torque will act and the vehicle will move in the desired direction. To hold the quad- rotor at a stationary position at some height constant rpm of all rotors has to be maintained. This signal is given by the controller from some distance, which is received by the, and then it processes the signal and drives the motor via the flight controller and drives the rotors. A quad- rotor is equipped with a high quality camera for photography and video shooting during surveillance. Since a quad rotor is manoeuvring in air, the wind may exert a drag force and take it along with it and the quad rotor may hit any obstacle or inspection objects. To avoid this, it is equipped with the ultrasonic sensors which is capable of sensing the obstacle and realize collision avoidance between wall or any object.

The Impact of Pump Speed and Blood Pressure Optimization on Severe Aortic Valve Insufficiency with Left Ventricular Assist Device: A Mock Loop Study

It is cumbersome to medically optimize the RPM setup and afterload adjustment for patients with significant aortic valve insufficiency (AI) with left ventricular assist device (LVAD). Limited amount of information is available regarding the optimal RPM setting or afterload adjustment without adverse effect on the degree of AI. All measurements were performed using a mock circulatory system with a dilated silicone LV model attached to a HeartMateII LVAD (Abbott Labs). Baseline condition was established with 17% ejection fraction, 62 bpm heart rate, LVAD set at 8,800rpm pump flow and 90 mmHg systemic aortic pressure, followed by testing at 8,800 and 9,200 rpm, and two systemic aortic pressure conditions (90 and 80 mmHg at 8,800 rpm). Severe AI was created with a small 3-D printed stent which was nonobstructive to forward flow but prevented the leaflets from fully closing. LVAD, aortic valve and systemic flow were recorded in each situation. Q ratio was calculated with LVAD flow/systemic flow, which represented an efficiency of LVAD flow contribution to the systemic flow. With the constant circuit afterload at 90mmHg, an RPM increase from 8,800 RPM to 9,200 resulted in systemic flow increase by 21% (2.27 to 2.74 L/min) with a 16% increase in LVAD flow (3.09 to 3.58 L/min), similar aortic valve flow (-0.82 to -0.84 L/min) and improvement in Q ratio (1.36 to 1.31). The regurgitant flow was similar in 8,800 vs. 9,200 (-0.86 vs. -0.83 L/min) in the severe AI setting. With the constant RPM at 8,800, an afterload reduction by 10 mmHg resulted in an increase of the systemic flow by 28% (2.27 to 2.91 L/min) with a LVAD flow increase of 14% (3.09 to 3.52 L/min), aortic valve flow increase of 23% (-0.82 to -0.61 L/min) and improvement in Q ratio (1.36 to 1.21). The alteration in the regurgitant flow was minimal between 90mmHg vs. 80mmHg afterload (-0.86 to -0.81 L/min). Both RPM increase and afterload reduction increased systemic flow and LVAD flow with improved Q ratio. The regurgitant flow stayed constant either with RPM increase or afterload reduction with the fixed regurgitant valve area. This mock-loop study suggests that both afterload reduction and RPM increase should improve systemic flow without increasing the degree of AI after LVAD implant.

Prediction of rock properties using grinding characteristics of ball mill

Knowledge of physico-mechanical properties of rocks is essential starting from the preliminary exploration to processing in mining projects. The strength properties of rocks considered necessary for mine planning and design, selection of equipment, use of suitable processing technique, etc. Sophisticated laboratory facilities are required to determine various properties of rocks using some international standards like ISRM, ASTM, etc., which is time consuming and costly affair. In this study, an attempt is to predict some of the rock properties like density, tensile strength using grinding characteristics of ball mill. Laboratory experiments conducted on samples of granite, limestone, slate and BHQ varying different parameters like quantity of feed, charge ratio, size of balls, grinding time, etc., at constant RPM of ball mill. Grinding characteristic curves used to obtain 25%, 50%, 80% cumulative passing sieve sizes. In addition, laboratory experiments carried out to find physico-mechanical properties like density, tensile strength, Protodyakonav's strength index, rebound hardness number. Regression analysis carried out with the data obtained from experiments.