Burner Assembly Research Articles

Fire testing methodology to develop solutions for storage and ceiling heights exceeding laboratory limits

The maximum ceiling height of the FM Global laboratory is 18.3 m. Therefore, fire protection solutions for warehouses with taller ceilings cannot be directly validated through full-scale testing. This work develops a methodology to obtain the key processes of fire growth, spray-plume interaction, and fire suppression response for an 18.9 m high roll-paper storage under a 24.4 m tall ceiling. The proposed methodology uses a heptane burner assembly at the base of the commodity array to match the fire heat release and growth rate to that of a taller storage exceeding lab capability. The burner assembly included six heptane burners and two air ducts. A series of experiments was conducted to characterize the burner design, model the fire growth in the free-burn stage, and validate controlled and uncontrolled fires in terms of the number of activated sprinklers. A final large-scale fire test used a 12.8 m high storage of Kraft paper with the burner assembly under an 18.3 m tall ceiling to validate protection recommendations for Kraft paper stored 18.9 m high under a 24.4 m tall ceiling. The test demonstrated full suppression using K360 (K-factor, lpm/bar1/2), fast response, pendent sprinklers with a temperature rating of 74 °C, supplied with a water pressure of 8.3 bar.

Effects of mechanically-induced oscillations on soot formation and flame temperature in laminar diffusion flames of ethylene

An experimental study was performed to measure the effects of flame oscillations on soot concentration and flame temperature in co-flow laminar diffusion flames of ethylene. One novel aspect of this study is that flame oscillations were mechanically induced by moving the burner assembly in a reciprocating motion with an industrial computer-controlled linear stage. Motor speed was used to control the oscillation frequency. The peak-to-peak oscillation amplitude was defined as stroke, which was then used to calculate the Strouhal number. Oscillation frequencies of 5‒20 Hz and peak-to-peak amplitudes of 0.5‒3 mm were studied. At 1 mm peak-to-peak oscillation amplitude, flame oscillations switched from tip flickering type to tip-clipping type oscillations above 10 Hz. Time-averaged soot concentration increased from its value in the steady-state flame when the flame was perturbed by small oscillation frequencies and amplitudes but then decreased as the oscillation intensity was increased. The peak time-averaged soot volume fraction was 9.5 ppm in the steady-state flame and 4.5 ppm at a peak-to-peak oscillation amplitude and an oscillation frequency of 1 mm and 20 Hz, respectively. Similarly, the peak soot volume fraction was 5.8 ppm at a peak-to-peak oscillation amplitude and an oscillation frequency of 3 mm and 10 Hz, respectively. The time-averaged flame temperatures were in the range of 1500‒2000 K. The low-temperature zone was observed at the flame core in the steady-state flame and for low-intensity oscillations, and at the flame tip for high-intensity oscillations. The literature has discrepancies on how flame oscillations affect the total soot loading in ethylene flames. Our results show that the total soot loading increased by about 10% from steady-state to low-intensity oscillations, then slightly decreased as either oscillation frequency or amplitude was increased. The effects of increasing the oscillation frequency or amplitude were similar and well captured by the revised Strouhal number.

Pilot impact on turbulent premixed methane/air and hydrogen-enriched methane/air flames in a laboratory-scale gas turbine model combustor

The impact of pilot flame operation on the combustion of pure methane and hydrogen-enriched methane (H2/CH4: 50/50 in vol%) fuels was investigated in a gas turbine model combustor under atmospheric conditions. The burner assembly was designed to mimic the geometry of an industrial burner, the Siemens DLE Burner, in which a concentric annular ring equipped with pilot flame burners is implemented in the dome of the combustor. Two pilot burner configurations have been investigated: a non-premixed and a partially premixed pilot arrangement. The performance of the pilot burners was evaluated for varying Reynolds number (Re) and H2 enrichment. High-speed OH∗ chemiluminescence imaging, as well as simultaneous planar laser-induced fluorescence measurements of the OH radicals and formaldehyde (CH2O) were used for evaluating the dynamics and structures of the flames for different conditions. Furthermore, emission measurements were carried out to determine the influence of hydrogen dilution on the NOx and CO emission levels. The main findings are (a) the effect of the pilot flame is sensitive to the Reynolds number of the main flame and the type of the pilot flame, (b) the stability range becomes narrower with increasing hydrogen ratio, due to the tendency to flashback, (c) non-premixed pilot flames lower the NOx and increase the CO emissions, albeit rather small differences in the emissions have been detected, and (d) the NOx and CO emissions become significantly lower with increasing hydrogen ratio.

An Investigation of Rotary Cup Burner Assembly with Three Vehicle-Mounted Cooking Stoves by Numerical Evaluation Method

The adaptability of vehicle-mounted heating systems that include burner and stove remarkably influences the system efficiency, heat flux uniformity, and pollutants emission. In this work, the performance of a rotary cup burner assembly with three different cooking stoves was investigated using ANSYS Fluent software based on five factors of thermal efficiency, heat transfer intensity, heating uniformity, CO emissions, and flue gas outlet temperature. The Eulerian-Lagrangian method was used to perform the diesel spray, and the shear stress transfer k-ω turbulence model and the probability density function model were employed to simulate the turbulent combustion. Based on the simulation results, the performance pentagon of the above five factors was constructed to evaluate the comprehensive performance of the new rotary cup burner system. The rotary cup burner had a good performance when it is used in two staple food stoves and a subsidiary food stove. In staple food stove A, its higher furnace increased the heat exchange area of the vessel, while the higher fireboard of staple food stove B caused a higher heat transfer intensity at the bottom of the vessel. However, the higher fireboard also led to higher CO emissions. In consideration of these two factors, the thermal efficiency of stove A was about 7% higher than that of stove B. Different from the staple food stove, the furnace of subsidiary food stove C had better wrapping to the bottom of the boiler so that it had the highest heat transfer intensity. The obtained performance pentagon shows that the comprehensive adaptability performance of stove A was the best and that of stove B was the worst, which is mainly caused by the height of the fireboard and the shape of the vessel. This research guides the optimization of the heating system and promotes the application of the rotary cup burner.

Particle dynamics in a gas assisted coal combustion chamber using advanced laser diagnostics

Coal combustion is strongly influenced by the interaction of gas phase turbulence, particle dynamics and chemistry. To advance the understanding of these mutually coupled processes, experiments under well-controlled inflow and boundary conditions are needed that provide access to non-intrusive multi-parameter measurement techniques. Following this idea, in this work gas-assisted coal flames with power up to 40 kWth are investigated in an optically accessible combustion chamber including a quartz glass quarl of the swirl burner assembly. A Two-phase particle image/tracking velocimetry (PIV-PTV) technique is applied for the first time in coal combustion to measure simultaneously velocities of small and large particles. Due to the wide particle size distribution of the grinded coal small particles can be used as tracers for the gas flow while the velocity of large particles can be measured with particle tracking velocimetry (PTV) simultaneously. For this purpose Mie-scattering is imaged by a single camera. Large and small particles are separated in the post-processing based on apparent size and signal intensity of each particle individually. By measuring quasi-simultaneously laser-induced fluorescence of intermediate hydrocarbons released from coal particles during their devolatilization process, regions of intense pyrolysis are identified. Flames operated with different coal types and thermal powers in air and oxy-fuel atmospheres are compared to each other. Additionally, advantages and limits of the measurement techniques are discussed in the context of coal combustion.

Computational Fluid Dynamic Analyses of Flow and Combustion in a Domestic Liquified Petroleum Gas Cookstove Burner—Part I: Design Optimization of Mixing Tube–Burner Assembly

Abstract Liquefied petroleum gas (LPG) is commonly used in domestic kitchen due to its low health and environmental impacts and high heat content compared to other traditional fuels. The growing demand of LPG, notwithstanding its limited reserve, influences the need for performance improvement of the LPG cookstoves. In an LPG cookstove, the fuel–air mixture is prepared in a self-aspirated burner, and burns as a rich premixed flame above the burner. The fuel–air ratio of the reactant mixture influences the burning characteristics and thermal efficiency of the cookstove. This part of work deals with a numerical study of flow and mixing characteristics in the mixing tube and burner assembly of a domestic LPG cookstove. The fuel is injected axially through a narrow nozzle inside the mixing tube causing entrainment of ambient air through the side ports and the end port. The effects of different side-port geometry, nozzle position, inlet fuel pressure, and nozzle throat diameter on the air ingress have been systematically investigated, and the optimum design has been identified. Results of the study provide important information on the design of the practical nozzle and mixing tube assembly of high-efficiency LPG stoves.

High Cycle Fatigue Failure of Burner Feeder Line in a Heavy-duty Gas Turbine Engine

Abstract A number of fuel gas supply pipes or feeder lines of heavy-duty gas turbine engines for power generation were found cracked in two sister engines of a power plant, this after approximately 100 000 operating hours. Cracks originated from the outer diameter (OD) of the feeder pipes, at the fusion line of the fillet weld that joined the subject pipes to the main burner bodies. The incident components failed by high cycle fatigue (HCF) fracture. The failure mechanism is purely mechanic. No evidence of corrosion or any other contributing mechanism was found. Design, manufacture, such as welding and coating, burner assembly, and burner installation are all unrelated to the failure. The root cause of the failure is excessive dynamic service loading.

An Influence of a Fluidic Oscillator Insertion in a Swirl-Stabilized Burner on Turbulent Premixed Flame

A series of experiments were performed on a vertical EV burner with a constant coflow air of 873 L/min to generate turbulent lean premixed flow in order to study the impact of the addition of acetylene/argon mixture to the liquefied petroleum gas (LPG) on the temperature field and flame structure. The fluidics mechanism was inserted at a fixed position inside the entry section of the EV burner assembly. The flow rates of fuel (LPG/C2H2/Ar) and air were measured using calibrated rotameters. The different volume ratios of the fuel constituents were admitted via three solenoid valves and monitored using a labview program. The axial temperature profiles at different operating conditions were measured using (type S) thermocouple. Flame images were obtained—before and after fluidics insertion—using a high-resolution digital camera. The experimental program aims at identifying and analyzing the changes in flame characteristics resulting from the insertion of fluidics while considering different proportions of the fuel constituents) (including pure LPG, as a reference case). The results obtained indicate the following: it was noticed that in most cases of pure LPG only and other mixtures, the images show increase in the length of the flame and decrease of its luminosity as a result of higher degrees of swirl due to the fluidics insertion while the temperature profiles of the different flames were changed. It was indicated that NOx trend was decreased by 52% while the combustion efficiency was improved by 2.5%.

Evaluating thermoacoustic properties of heating appliances considering the burner and heat exchanger as acoustically active elements

Heat exchangers are an essential constituent part of many combustion systems. The thermoacoustic instability in such systems is a common problem and it has been studied extensively. However, the heat exchanger has not gained much attention in the field of combustion thermoacoustics, leading to a lack of knowledge about the thermoacoustic interactions between the burner and the heat exchanger. In this paper, a modeling approach is introduced to study these interactions in an academic representation of a heating appliance, comprised of a perforated slit burner and a tube heat exchanger. Both elements are considered thermally and acoustically active. A CFD model is used in a two-dimensional domain to simulate the response of the system to small amplitude broadband velocity perturbations. The thermochemical and acoustic coupling between the burner and the heat exchanger is investigated and a method is introduced to decouple their effects and study them separately. The extents to which this method is valid are addressed by varying the distance between the elements. Results show that as long as the flames do not impinge on the heat exchanger surface, a linear network modeling approach can be applied to construct the acoustic response of the composed configuration from the responses of its constituting elements. This approach requires registering the average velocity on a properly chosen intermediate plane between the burner and heat exchanger. Choosing this plane may be to some point difficult, i.e. when the burner and heat exchanger are close and cannot be considered independent. Moreover, when flame impingement occurs, the interactions between the flame and heat exchanger affect their individual thermoacoustic behaviors and the burner plus heat exchanger assembly needs to be considered as one coupled acoustic element. Particularly, flame impingement changes the phase of the heat absorption response of the heat exchanger and it may significantly alter the acoustic properties of the coupled assembly. The physics lying behind the effects of such interactions on the thermoacoustics of the system is discussed. The obtained results signify that a correct stability prediction of an appliance with burner and heat exchangers requires considering active thermoacoustic behavior of both elements as well as their interactions.

Ultra-low NOx emissions from catalytic hydrogen combustion

The objective of this work is to determine the nitrogen oxide emission in the flue gas of a catalytic hydrogen combustion process, operating without premixed hydrogen and air supply. The study was investigated on a novel designed gas under glass stove top burner, suitable for domestic kitchen applications. The basic catalytic burner assembly consists of two platinum coated silicon carbide (SiC) foam disks with a diameter of 150 mm, a thickness of 10 mm and a porosity of 60 and 80 pores per inch (ppi) respectively. The two catalytic SiC disks are stacked with 10 mm space between for a uniform air feeding and distribution. Hydrogen is supplied from below the assembly and air is blown in between the two Pt coated catalytic SiC disks, leading to a homogeneous air distribution and thus a uniform catalytic reaction of hydrogen and air. Tests are performed at hydrogen flow rates of 5, 10 and 15 Nl/min, equivalent to 0.9, 1.8, 2.7 kW power, the hydrogen to oxygen ratios (φ) were fixed to 0.66, 0.5 and 0.33 respectively. Ultra-low nitrogen oxide emissions of 0.09 ppmv to 9.49 ppmv, equivalent to 0.007 to 0.37 mg/kWh are achieved with this novel developed catalytic combustion design. These values are significantly lower than the present EU regulation of 56 mg/kWh for combustion processes of gaseous fuels for heating applications. This result shows the very high potential of converting hydrogen to heat without harmful exhaust gases for a broad domestic application in decarbonised gas grids or stationary power to gas applications.

AN INVESTIGATION OF ARGON GAS ADDITIVES TO LPG ON THE TURBULENT LEAN PREMIXED FLAME CHARACTERISTICS FOR EV BURNER

A sets of experiments were done on a vertical environmental (EV) burner with fixed coflow air of 873 Lit /min to ensure turbulent lean premixed flow in order to study the effect of additon of argon mixture to the Liquefied Petroleum Gas on the temperature distributions and flame structure. The environmental (EV) burner assembly was fixed vertically in the test rig to scan the flame radially and axially. The flow rate of fuels, diluent and air were measured using rotameters.The whole supply lines were calibrated. The mixture of gases, air were injected through mixing pipes controlled with solenoid valves handled with a Labview program.The combustion flame was in room atmospheric conditions. The turbulent flame axial, radial temperature profile was measured using a shielded Platinum thermocouple type S. Flame images were taken using high resolution Canon 6D digital camera with high resolution lens .The fuel used was mixtures of different fuels of LPG, Argon. The choice of the different investigated cases was based on flame stability. The axial, radial distributions of mean gas and exhaust temperature,smoke number,NOx and combustion efficiency, are presented and analyzed for selective cases.The results obtained indicate the following: for pure LPG flames the images show short light blue flames at low flow rates and with progressive increase of the fuel flow rate this color changed to dark blue flame then to yellowish and white luminous zone.The exhaust temperature ranges was increasing with increasing of fuel flow rate of LPG. By Ar addition the flame luminosity decreases with the increase of Ar dilution, also the flame length increased in all runs with the progressive increase of Argon flow rate while decreasing the soot formation, while the NOx trend, exhaust temperature and combustion efficiency decreased by increasing Argon percentage addition.

Dynamic balancing and experience during the development of a single cylinder Beta-configuration Stirling engine using rhombic drive

The present work starts with analysis, and culminates in the development of engine. Hydrogen is selected as working fluid due to its favorable thermodynamic and thermo-physical properties. During fabrication and sub-assembly engine was run by electrical motor as in motoring test. It provided cooling at the cylinder head and confirmed that all the system components were performing well under low charge pressure. Dynamic balancing analysis is done to eliminate unbalanced couple. The same was included in the system by removal of pre-decided part of the gears which also acted as the flywheel. The engine performance was demonstrated by operating the centrifugal pump. LPG burner assembly designed, especially for this Stirling engine, is successfully demonstrated. Preliminary trials for approximately 3–5 min, with loading condition in engine mode, with LPG were conducted. The flame temperature near the cylinder head was maintained at about 1100 K. It needs to be ensured that uniform but sufficient heat input should be provided. In short, an experimental set-up is built in accordance with geometrical dimensions specified in the theoretical design. Theoretically predicted performance and experimental results have been compared and validated for the developed unit for a particular set of operating parameter with H2.

Energy-Efficient Structure for the Lining of the Burner Assembly in a Glass-Founding Furnace

The linings currently used for the channel of the burner assembly in glassmaking furnaces are analyzed and an original new design is presented for the lining’ structure. Use of the new lining cuts heat loss to the environment in half.

An experimental investigation of the interaction of swirl flow with partially premixed disk stabilized propane flames

The present work describes the experimental investigation of reacting wakes established through fuel injection and staged premixing with air in an axisymmetric double cavity arrangement, formed along three concentric disks, and stabilized in the downstream vortex region of the afterbody. The burner assembly is operated with a co-flow of swirling air, aerodynamically introduced upstream of the burner exit plane, to allow for the study of the interaction between the resulting partially premixed recirculating afterbody flames with the surrounding swirl. At low swirl the primary afterbody disk stabilizes the partially premixed annular jet in the downstream reacting wake formation region. As swirl increases, a system of two successive vortices emerges along the axis of the developing wake; the primary afterbody vortex is cooperating with an adjacent, swirl induced, central recirculation zone and this combination further promotes turbulent mixing in the hot wake. Complementary measurements of the counterpart isothermal turbulent velocity fields provided important information on the near wake aerodynamics under the interaction of the variable swirl and the double cavity produced annular jet stabilized by the afterbody. Under reacting conditions, measurements of turbulent velocities, temperatures and statistics together with an evaluation of the exhaust emissions were performed using LDV, thin digitally-compensated thermocouples and gas analyzers. A selected number of lean and ultra-lean flames were investigated by regulating the injected fuel and the air supply ratio, while the influence of the variation of the imposed swirl on wake development, flame characteristics and emission performance was documented for constant fuel injections. The differences and similarities between the present partially premixed stabilizer and other types of axisymmetric configurations are also highlighted and discussed.

Thermal performance of a premixed impinging circular flame jet array with induced-swirl

An array of three identical premixed butane–air-fired impinging circular flames with induced-swirl operating at low-pressure and low-Reynolds-number was developed. A swirling motion was imparted successfully to the flame by forcing the butane/air mixture through a specially designed burner assembly before ignition. The burner assembly consisting of a conical base and a nozzle tube into which a cylindrical bar fabricated with three spiral channels was inserted. Its thermal performance was compared with that of a similar impinging flame jet system without induced-swirl. Effects of varying the Reynolds number and the equivalence ratio of the butane/air mixture and the nozzle-to-plate distance on the thermal performance of each of these two impinging flame jet systems were studied. Experiments were conducted with different combinations of Reynolds number, equivalence ratio and nozzle-to-plate distance. In the present investigation, the Reynolds number ranged from 500 to 2500, the equivalence ratio ranged from 1.0 to 1.8 and the nozzle-to-plate distance ranged from 20 mm to 30 mm. To facilitate comparison, flame shapes of both impinging flame jet systems were also visualized by a high speed digital camera system. The comparison showed that the array of three small-scale, low-pressure and low-Reynolds-number premixed butane–air-fired impinging circular flame jets could enhance its thermal performance, with respect to heat transfer characteristics and blow-out limits, by incorporating an induced-swirl. The performance enhancement increased with increasing Reynolds number or equivalence ratio, but decreased with increasing nozzle-to-plate distance.

Stability characteristics and flowfields of turbulent non-premixed swirling flames

A simple, yet representative, burner geometry is used for the investigation of highly swirling turbulent unconfined, non-premixed, flames of natural gas. The burner configuration comprises a ceramic faced bluff-body with a central fuel jet. The bluff-body is surrounded by an annulus that delivers a swirling primary flow of air. The entire burner assembly is housed in a wind tunnel providing a secondary co-flowing stream of air. This hybrid bluff-body/swirl burner configuration stabilizes complex turbulent flames not unlike those found in practical combustors, yet is amenable to modelling because of its well-defined boundary conditions. Full stability characteristics including blow-off limits and comprehensive maps of flame shapes are presented for swirling flames of three different fuel mixtures: compressed natural gas (CNG), CNG–air (1:2 by volume) and CNG–H2 (1:1 by volume). It is found that with increased fuel flow, flame blow-off mode may change with swirl number, Sg. At low swirl, the flame remains stable at the base but blows off in the neck region further downstream. At higher swirl numbers, the flames peel off completely from the burner's base. Swirling CNG–air flames are distinct in that they only undergo base blow-off. In the low range of swirl number, increasing Sg causes limited improvement in the blow-off limits of the flames investigated and (for a few cases) can even lead to some deterioration over a small intermediate range of Sg. It is only above a certain threshold of swirl that significant improvements in blow-off limits appear. Six flames are selected for further detailed flowfield and composition measurements and these differ in the combination of swirl number, primary axial velocity through the annulus, Us, and bulk fuel jet velocity, Uj. Only velocity field measurements are presented in this paper. A number of flow features are resolved in these flames, which resemble those already associated with non-reacting swirling flows of equivalent swirl obtained with the present burner configuration. Additionally, asymmetric flowfields inherent to some flames are revealed where the fluidic centreline of the flow (defined in the two-dimensional (U–W velocity pair) velocity field by the ⟨ω⟩ = 0 tangential velocity contour), meanders strongly on either side of the geometric centreline downstream by about one bluff-body diameter. Flow structures revealed by the velocity data are correlated to flame shapes to yield a better understanding of how the velocity field influences the flames physical characteristics.

Acoustically pulsating burner with integral adjustable Sondhauss thermoacoustic elements

An acoustically pulsating burner assembly which includes an elongated outer tube, a fuel supply means located within the tube, and utilizes one or more integral axially adjustable Sondhauss thermoacoustic tubular elements to generate pulsations within the burner. The acoustic pulsations are generated inside the axially movable closed end tube element provided within the burner, and these vibrations promote more efficient combustion of the fuel so as to reduce undesired emissions in the combustion products. If desired, multiple thermoacoustic tubular elements of different lengths can be advantageously used to generate pulsations of different frequencies within the burner assembly. The burner assembly is located in a furnace windbox, and can be adapted for combusting gas, oil or particulate fuels such as coal.

Blowout Limits of a Jet Diffusion Flame in the Presence of Small Surrounding Jet Pilot Flames

The blowout limit of a methane jet diffusion flame is examined in the presence of a number of much smaller pilot jet flames of different fuels arranged within an experimental burner assembly in a co-flowing stream of air. It is shown that the blowout limit of the central jet flame can be extended very appreciably by increasing the flow rate through the smaller pilot jets. The basis for this extension to the blowout limit and the role of some changes in the operating parameters are discussed. It is suggested that the extension to the blowout limit observed is due mainly to the thermal contribution of the pilot jet flames.

Determination of ruthenium in organic solutions by flame atomic absorption spectrometry, with ethanol and methyl isobutyl ketone as solvents

A flame atomic absorption spectrometric method is described for the determination of ruthenium in organic solutions containing toluene, 1-hexene, 1-heptanol and 1-heptanal. Ethanol and methyl isobutyl ketone (MIBK) were tested as solvents. In addition to burner position and acetylene flow, the composition of the organic solution significantly affected the absorbance. Ethanol has several advantages over MIBK as a solvent: sensitivity is better and the detection limit lower, the smell is less unpleasant, the burner and chamber assembly keep cleaner and the burner position is less critical. Ethanol is an excellent solvent for the analysis of hydroformulation solutions containing more than 50 μg/ml of ruthenium. Synthetic and real hydroformulation solutions containing 50–2000 μg/ml Ru were successfully analysed after dilution with appropriate amounts of ethanol and toluene.

Determination of rhodium in organic solutions by flame atomic absorption spectrometry, with methyl isobutyl ketone and ethanol as solvents

A flame atomic absorption spectrometric method for the determination of rhodium in organic solutions containing toluene, 1-hexene, 1-heptanol and 1-heptanal is described. Methyl isobutyl ketone (MIBK) and ethanol were used as solvents and 1-heptanal as buffering agent. In addition to burner position, the composition of the organic solution significantly affected the absorbance. The recovery of 5 μg/ml rhodium was only 60% in a solution containing 75% MIBK, 20% toluene and 5% hexene, but improved as the ratio of alcohol or aldehyde to hexene increased. When the amount of hexene was reduced to zero and 5% heptanol, 5% heptanal or 2.5% heptanol + 2.5% heptanal was used instead, recoveries were 97%, 92% and 95%, respectively. The recoveries of 10 μg/ml rhodium in solutions containing 75% ethanol, 20% toluene and 2.5% hexene + 2.5% heptanol, heptanal or their mixtures were 97%, 104% and 103%, respectively. Ethanol has several advantages over MIBK as a solvent: it is cheaper, the smell is less unpleasant, the burner and chamber assembly keep cleaner and sensitivity is slightly better.